1) Do you see the airplane begin to wander in 8x+ time compression if you use PMDG's Auto-Time-Compression feature?
Yes, as long as the plane doesn't go above x4 its fine.
2) Do you see the airplane begin to wander in 8x+ time compression if you manually set the time compression using the FSX menu or key commands?
3) Do you have FSUIPC installed?
3a) Which version is installed?
3b) Have you tried deleting your FSUIPC config file and letting it rebuild?
4) Have you tried deleting your FSX.CFG file and letting it rebuild?
5) Do you have Lockheed Martin Prepar3d installed on this machine?
6) When the airplane begins to wander, watch the HEADING ROSE on the NAV DISPLAY very carefully. Is it rotating in the proper direction and remaining in sync with the airplane heading? If not- we need to know.
No, the ND thinks its maintaining the correct heading.