Solved the problem  :)
Just gone on the right-click on the application, then properties, compatibility and run with the compatibility with windows xp Service Pack 3 ;)

Thanks everyone for your support!! I'll see the other threds, but here's the log:

16:57:04.0

---===+++===---

16:57:04.0 Starting Plan-G (W7 edition), build 3.1.2.101
16:57:04.0 OS is Microsoft Windows NT 6.1.7600.0
17:00:13.0

---===+++===---

17:00:13.0 Starting Plan-G (W7 edition), build 3.1.2.101
17:00:13.0 OS is Microsoft Windows NT 6.1.7600.0
17:00:13.1 InitDataFolder
17:00:13.1 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_FSX.sdf
17:00:13.1 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_FS9.sdf
17:00:13.1 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_XPX.sdf
17:00:13.1 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_P3D.sdf
17:00:13.1 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_NAVI.sdf
17:00:13.1 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\UserWaypoints.sdf
17:00:13.1 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\MEF.sdf
17:00:13.6 Map tiles cache: C:\Users\cwo_gp\AppData\Local\GMap.NET\
17:00:13.7 Program in: D:\Plan-G v3
17:00:13.7 Data in: C:\Users\cwo_gp\Documents\Plan-G Files
17:00:13.7 IsDataLoaded: FSX
17:00:13.7 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_FSX.sdf
17:00:14.4 This build: 312101 Latest build: 312101
17:00:14.4 Starting timer
17:00:14.4 DownloadCurrentMetars thread started
17:00:14.4 Metar14Z.TXT started
17:00:14.4 Metar15Z.TXT started
17:00:14.4 lTAF06Z.TXT started
17:00:14.4 sTAF12Z.TXT started
17:00:15.1 sTAF12Z.TXT done
17:00:15.1 lTAF12Z.TXT started
17:00:15.8 sTAF06Z.TXT started
17:00:16.5 IsDataLoaded: FSX
17:00:16.5 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_FSX.sdf
17:00:16.5 IsDataLoaded: FS9
17:00:16.5 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_FS9.sdf
17:00:16.6 IsDataLoaded: P3D
17:00:16.6 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_P3D.sdf
17:00:16.6 IsDataLoaded: XPlane
17:00:16.6 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_XPX.sdf
17:00:17.0 sTAF06Z.TXT done
17:00:17.1 Stopping timer
17:00:17.1 StartMap
17:00:17.1 Connection string: metadata=res://*/Data.FSData.csdl|res://*/Data.FSData.ssdl|res://*/Data.FSData.msl;provider=System.Data.SqlServerCe.3.5;provider connection string='Data Source=|DataDirectory|\Data\PlanG3_FSX.sdf'
17:00:17.4 NdbsInBounds 11
17:00:17.6 VorsInBounds 9
17:00:17.8 AirportsInBounds 27
17:00:18.7 AirspaceInBounds 64
17:00:18.8 NdbsInBounds 11
17:00:18.8 VorsInBounds 9
17:00:18.8 AirportsInBounds 27
17:00:18.8 AirspaceInBounds 64
17:00:19.6 Metar15Z.TXT done
17:00:21.0 lTAF12Z.TXT done
17:00:21.0 lTAF06Z.TXT done
17:00:23.9 Metar14Z.TXT done
17:00:23.9 DownloadCurrentMetars done
17:00:24.4 ProcessMetars done
17:00:29.8 _Backstage_IsOpenChanged: True
17:00:31.4 _Backstage_IsOpenChanged: False
17:00:31.5 OpenFlightPlan_Executed: Plan_G
17:00:31.5 OpenFlightPlan 1
17:00:31.5 Dialog created
17:00:31.5 Filter = Plan-G Flight plan files (*.plg)|*.plg|FSX / FS9  Flight plan files (*.pln)|*.pln|X-Plane FMS flight plan files (*.fms)|*.fms|v3 Aircraft Breadcrumb Trail files (*.IGC)|*.IGC|v2 Aircraft Breadcrumb Trail files (*.txt)|*.txt
17:00:31.5 fullpath = C:\Users\cwo_gp\Documents\Plan-G Files
17:00:31.5 path exists
17:00:31.5 Calling ShowDialog() C:\Users\cwo_gp\Documents\Plan-G Files
17:00:31.6 ShowDialog() returned false
17:00:34.2 OpenFlightPlan_Executed: Plan_G
17:00:34.2 OpenFlightPlan 1
17:00:34.2 Dialog created
17:00:34.2 Filter = Plan-G Flight plan files (*.plg)|*.plg|FSX / FS9  Flight plan files (*.pln)|*.pln|X-Plane FMS flight plan files (*.fms)|*.fms|v3 Aircraft Breadcrumb Trail files (*.IGC)|*.IGC|v2 Aircraft Breadcrumb Trail files (*.txt)|*.txt
17:00:34.2 fullpath = C:\Users\cwo_gp\Documents\Plan-G Files
17:00:34.2 path exists
17:00:34.2 Calling ShowDialog() C:\Users\cwo_gp\Documents\Plan-G Files
17:00:34.3 ShowDialog() returned false
17:00:36.9 Initiating SimConnect connection.
17:00:36.9 Connect
17:00:36.9 SimConnect.Connect - Remote. Mode = IPv4 Server = localhost Port = 0
17:00:37.0 SIMCONNECT_RECV_OPEN
17:00:37.0 sc_OnRecvOpen Connected to FSX
17:00:37.0 Connected to sim
17:00:37.0 Traffic update:51 planes
17:00:37.3 Transponder: 4608
17:00:37.3 NdbsInBounds 5
17:00:37.5 VorsInBounds 6
17:00:37.7 AirportsInBounds 7
17:00:37.8 AirspaceInBounds 72
17:00:39.8 NdbsInBounds 6
17:00:39.8 VorsInBounds 8
17:00:39.9 AirportsInBounds 7
17:00:39.9 AirspaceInBounds 80
17:00:45.5 _Backstage_IsOpenChanged: True
17:00:47.2 _Backstage_IsOpenChanged: False
17:00:52.6 NdbsInBounds 6
17:00:52.6 VorsInBounds 9
17:00:52.7 AirportsInBounds 9
17:00:52.7 AirspaceInBounds 90
17:00:55.4 NdbsInBounds 5
17:00:55.4 VorsInBounds 9
17:00:55.4 AirportsInBounds 11
17:00:55.5 AirspaceInBounds 88
17:00:59.0 _Backstage_IsOpenChanged: True
17:01:00.7 Cleanup
17:36:42.6

---===+++===---

17:36:42.6 Starting Plan-G (W7 edition), build 3.1.2.101
17:36:42.6 OS is Microsoft Windows NT 6.1.7600.0
17:36:42.7 InitDataFolder
17:36:42.7 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_FSX.sdf
17:36:42.7 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_FS9.sdf
17:36:42.7 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_XPX.sdf
17:36:42.7 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_P3D.sdf
17:36:42.7 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_NAVI.sdf
17:36:42.7 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\UserWaypoints.sdf
17:36:42.7 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\MEF.sdf
17:36:43.2 Map tiles cache: C:\Users\cwo_gp\AppData\Local\GMap.NET\
17:36:43.4 Program in: D:\Plan-G v3
17:36:43.4 Data in: C:\Users\cwo_gp\Documents\Plan-G Files
17:36:43.4 IsDataLoaded: FSX
17:36:43.4 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_FSX.sdf
17:36:43.6 Starting timer
17:36:43.6 DownloadCurrentMetars thread started
17:36:43.6 lTAF06Z.TXT started
17:36:43.6 Metar14Z.TXT started
17:36:43.6 Metar15Z.TXT started
17:36:43.6 sTAF12Z.TXT started
17:36:44.3 lTAF12Z.TXT started
17:36:44.9 sTAF06Z.TXT started
17:36:45.1 sTAF12Z.TXT done
17:36:45.3 IsDataLoaded: FSX
17:36:45.3 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_FSX.sdf
17:36:45.3 IsDataLoaded: FS9
17:36:45.3 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_FS9.sdf
17:36:45.3 IsDataLoaded: P3D
17:36:45.3 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_P3D.sdf
17:36:45.3 IsDataLoaded: XPlane
17:36:45.3 Data Source = C:\Users\cwo_gp\Documents\Plan-G Files\Data\PlanG3_XPX.sdf
17:36:46.1 Stopping timer
17:36:46.1 StartMap
17:36:46.1 Connection string: metadata=res://*/Data.FSData.csdl|res://*/Data.FSData.ssdl|res://*/Data.FSData.msl;provider=System.Data.SqlServerCe.3.5;provider connection string='Data Source=|DataDirectory|\Data\PlanG3_FSX.sdf'
17:36:46.3 NdbsInBounds 5
17:36:46.4 VorsInBounds 9
17:36:46.5 AirportsInBounds 11
17:36:46.6 sTAF06Z.TXT done
17:36:46.7 AirspaceInBounds 88
17:36:46.7 NdbsInBounds 5
17:36:46.7 VorsInBounds 9
17:36:46.7 AirportsInBounds 11
17:36:46.8 AirspaceInBounds 88
17:36:49.0 userWaypointManager.OnLoaded start
17:36:49.0 DataChangedHandler clearing waypoints
17:36:49.1 userWaypointManager.OnLoaded end
17:36:50.6 lTAF06Z.TXT done
17:36:51.3 OnClosing
17:36:51.9 lTAF12Z.TXT done
17:36:52.0 Metar15Z.TXT done
17:36:54.9 Metar14Z.TXT done
17:36:54.9 DownloadCurrentMetars done
17:36:55.5 ProcessMetars done
17:51:43.6 DownloadCurrentMetars thread started
17:51:43.6 Metar14Z.TXT started
17:51:43.6 Metar15Z.TXT started
17:51:43.6 lTAF06Z.TXT started
17:51:44.6 sTAF12Z.TXT started
17:51:45.1 lTAF12Z.TXT started
17:51:45.3 sTAF12Z.TXT done
17:51:45.3 sTAF06Z.TXT started
17:51:46.0 sTAF06Z.TXT done
17:51:48.5 lTAF06Z.TXT done
17:51:50.3 lTAF12Z.TXT done
17:51:54.4 Metar15Z.TXT done
17:51:55.0 Metar14Z.TXT done
17:51:55.0 DownloadCurrentMetars done
17:51:55.7 ProcessMetars done
18:02:28.8 Cleanup

Hi folks!! I would like to ask a question about PlanG software. This is my problem: I've installed Plang v3.1.2 in my formatted PC (win 7 professional 64bit). Everything is good, but when I press a random button (for example to import some points, or to export a FlightPlan) no windows opens. The strange thing is that I've installed the SAME version of PlanG in the SAME OS in another PC with the SAME version of .NET Framework. I've tried to uninstall and reinstall it, I've tried to install the program out of Program Files (x86), to install it in another partition, but nothing happens. What should I do? Thanks for you support  :)