I had similar problem, but soon found the cure. My previous copy was set to run connected via FSUiPC, but the new one installed using the sim-connect option, I just clicked on the fsuipc option and it works fine now.

And boy do I love the PFD and AP, my Saitek AP Panel has stopped working, and this is much better, I do have multi monitors also which helps.

Many thanks Tim for the upgrade, will have to dig out my wallet shortly. ;D

Excuse me as I have been running PlanG with FSX on Win7-64 bit for a year or more, and never had any problems what ever with PlanG.
I just wonder what your hardware set up might be.
I use a quad cpu, nVidia Graphics, and dual 24" ws Monitors.

I feel I must add my few words of appreciation here.
Thanks very much Chef Tim for your masterful aid to flight sim enjoyment.
Since finding and using Plan-G my simming time has been much improved.
And as an Octogenarian the user friendliness is found to be very good.
Thanks Tim for your time, work, and interest in the subject.