I've tried to open these several ways (by eliminating plugins, etc).
Important to note that MOST of my X2 projects open, but about 20% are still not opening, and causing an instant crash on PLAY.
 
any updates on this?

It worked fine for me in the beginning. Just love X3! but...
 
However after updated to Windows 8.1 I do have some issues with plugins, crashing from time to time, can't even open some of my X2 projects. Works fine with a new project. Very annoying as I set up some templates in X2 that I want to use in X3. Work sometimes...
 
Waves plugins I had to do a fresh install of them. Seem that Sonar X3 seem to dislike my latest update of NativeInstruments Komplete 9 also.
 
I believe there will be an update soon X3c...