I can't answer your problem, but I think it is related to the problem I've been experiencing in the thread entitled "what happened?"
I didn't loose the whole project, just some events. This was after completing a render and twice when a render crashed the PC (that was the worse because I lost some audio events as well as video and stills).
I contacted SCS support but they seemed to think mine is an isolated case and suggest I do all the usual: make sure I am using the latest release ((9.0c), defrag the drive run the clean disk utility. stop non-essential programs and anti virus before rendering.
I am rendering again now and it seems to be going OK but this is disturbing
Sony Vegas Pro 9e
gallons of coffee