FSX still not saving flights, keeps crashing upon..

It seems that FSX keeps having problems when the application is shutdown. Otherwise, it runs beautifully, very good framerates. But when I close it down, Windows Vista gives a 'fatal error' message and then wants to restart FSX.

I'm a little confused on what's triggering it. I have done a 'repair re-install' of FSX and it doesnt seem to help.