Since your problem is caused by the wrap_oal.dll and it's an audio-related problem, if you can't fix it as explained in this thread, I don't see many other options that either reinstalling Windows from scratch, or eventually changing the audio card if it still continues after a completely fresh Windows installation.
The issue is, only a couple of people reported it, and several of them fixed it by reinstalling or updating the wrap_oal.dll, you are the only one that wasn't able to do anything about it so, either you did something wrong, or your audio driver is bugged beyond repair OR in YOUR specific system, you installed ANOTHER product (even not FSX-related) that caused problems with wrap_oal.dll only in your specific installation.
Searching "wrap_oal.dll" on Google, reports many problems with many different products so, it's nothing really related to GSX, it might happen with any other game out there.
