This sounds really ugly!

Sorry to hear this . .
However, have you tried ctrl+shift+restart Vegas. This DOES reset everything to factory defaults. You WILL loose your preference settings - no biggie, I sometimes have to do this if I have not cleaned my OS for sometime.
Try it and get back.
Have you done any housekeeping lately? I had a really bad case of 7% available use on my system drive this week.

Fool me!
I had temp proxy-nesting files and the like constipating the loading of my system. How free is your system drive? How much available space for your programs is there to thrash about in?
If needed, try cleaning up your drive/s. Switch off AV progs.
As a last thought there WAS a glitch with an ".exe" file . .what was it? it was something like -
wow . .. exe - or something like that? Others may remember. But that was
also hanging a Vegas load. But you may have a version of Vegas that is without that impediment. Dunno

?
- g