Project created on Sonar X2 causes it to freeze, but plays on Sonar 7??

I have a problem. I have created a project on X2 Producer, and it has been a work in progress for months now. Suddenly, it freezes X2 after loading when I try to press the play button. I eventually reinstalled X2 with the same result.
 
Desperate to not lose my work, I loaded up my old version of Sonar, (7) which doesnt officially run on Windows 7, and the project plays. I resaved it under a different file name and the newly saved file has the same effect on X2. - it hangs.
 
I thought it could be a VST effect that I am using that is native to X2 and doesnt run on 7 that may be the cause, but rather than go through every VST in safe mode start (there are a lot of them) I wondered if anyone had any other ideas?
 
Core i5, quad, 4 Meg Ram Win 7 Edirol UA-25

Try saving a new version of it and see if that opens it. If not, its a plugin and you will need to open it in safe mode to see what plugin is causing it. sure it takes time, but if you want to solve it, then you need to take the time to do it.
 
Also, Is it 32bit or 64bit? Sonar 7 and Sonar X2.
Have you installed all the X2 patches?
 
CJ

@ Scook Thanks, the audio engine is still running
@CJ, I did try save it under a new name, but with no luck, Also I am using X2 and & 7 32 bit versions. I have only loaded this patch:
 
 are there more?
 
Yes I thought I would have to try the safe mode approach.
 
@ Bob, thanks for this tip, I did not know about it and will try it