How to troubleshoot crashes of FS9 at EGLL?

I've spent this week trying to figure out why FS9 now usually crashes (freezes more or less irredeemably) on approach into EGLL. I get to within 1 nm to 8nm of landing and the sim freezes. I've tried it in the POSKY 742 and also the default 744. Same happens at Gatwick airport. Everywhere else in the world seems fine. Don't always get a freeze but about 80-90% of the time. Some folks at the UT forum think this might be an AI a/c issue and that perhaps one of the UT a/c has become corrupted for some reason or other. Earlier, I reduced AI to 0% and no freeze occurred. I then tried at 10% and all fine. When I raised AI to 35% and above, the freezes re-occurred.I don't really know how to troubleshoot this matter. How do I determine if it IS an AI a/c from UT doing this? How do I check an AFCAD (where do I check an afcad?!) or a bgl file. I am unfamiliar with the scenery gig and afcad management. My instal of UT is plain vanilla from CD-ROM, no online updates, no add-ons, it's always worked 100% great for me all over the world.Appreciate any further advice or assistance on this. Thanks!JS