When you completed your previous uninstalls, did you do a file search on your hard drive for the simconnect file? Sometimes it is corrupt upon install, but stays on your computer after the uninstall along with a couple of other FSX files. Then once you reinstall the FSX it does not replace the file, leaving you with the same corrupt file. You might want to do a manual search for it, if you find it, delete it, then run a repair install from your install disk to replace it. If that doesn't work, then find the file, delete it, then do a fresh install (although I know thats not what you want to hear.) Only other things I can think of is it might be your anti-virus software interfering with your setup. Try turning off your anti-virus software while you are installing FSX. I had that problem briefly when I first installed my Track IR. Turned out the Track IR wouldn't work due to my anti-virus program interfering with my simconnect. Hope this helps.