Hi, thanks for the replies.I still don't have my PC back, so cannot try anything yet. No, I only found out about the UIAUTOMATIONCORE.DLL probelm after the PC broke down, so that is something I can try, but my question was in reference to FS9: I didn't get the chance to start installing FSX before the PC failed. Is the UIAUTOMATIONCORE.DLL issue relevant to FS9 too? 95% of my flying is FS9, not FSX.I did install FS9 into its own directory, not even on the same disc as Windows 7 (both Win7 and FS9 were on a SSD). Elsewhere I have read that FS MUST be installed in the default folder or it won't work (but I take that with a pinch of salt). Installing away from Windows 7 didn't help with this issue in any case.It seems that it doesn't matter whether you have an nVidia or an ATI GPU installed - both vc10man and Bob are saying they have no problems. As things stand, I can't see any advantage to my switching to a Radeon HD card. Your setup is quite similar to mine Bob and you say you have no problems.. PMDG did tell me however that the problems I described were 'known issues' as I reported above. They suspect that the problem is (quote) "actually a Windows Driver Model (WDM) problem.. more than it is an Nvidia problem". When I finally get my PC back I shall install FS9 first and see if I get any problems switching between windowed and full-screen modes with an out-of-the-box installation. Then add a/c slowly and test after each one. I'll post results here, but looks like it's going to take some time for me even to get the PC returned. As if I didn't have enough frustrations without the PC giving out!Martin

Hi Martin.This may be something you have already tried, but have you tried disabling UAC?Martin. [Another Martin ]

Hi. Yes, UAC was switched off, but thanks.

Martin,I run FSX exclusively so I cannot comment on your problem as it relates to FS9. I can only say I have no issues with FSX, WIN 7 and my GTX480.

Re-ordered a PC, similar to the problem one (specs as per signature, below): just hoping this will be OK this time. I am going to reinstall everything really slowly, so I know exactly where the problems are. Fingers crossed.Martin

My guess is that if a 4xx nVidia card is blamed for the issues described then a) the plane is incorrectly written or 2) a system configuration issue is causing the issue.  Drivers play the most important role in a smooth running system.jja 

i am thinking of replacing my gtx260 with a gtx460 1gb. i will avoid ati cards because i couldn't get aa work with my 4870 1gbi hope you will be able to fix the problems you had.

i am thinking of replacing my gtx260 with a gtx460 1gb. i will avoid ati cards because i couldn't get aa work with my 4870 1gbi hope you will be able to fix the problems you had.

Me too, I just sold my GTX 260 and waiting for my GTX 460 ;)