FSX/Steam won't open all of a sudden

[Charlie98]

RE: Game rig in sig below...still running W7

For some reason, all a sudden, Flight Simulator X won't open in Steam. It worked fine 2 weeks ago, but now I get the splash screen, one core pegs out at 100%... and it sets there.

I've uninstalled/reinstalled both FSX and Steam, with no improvement.