Help! File won't open.

I'm having a strange problem with Sonar 4.0.2 (Producer). I have a large (lots of audio tracks) file I was just working on and Sonar locked up. In task manager it showed 100% CPU usage. I had to end the program. Now I can't get the file to open. It starts to open, but the windows remain empty and it locks up Sonar. Windows isn't locked up, but task manager shows 100% CPU usage. I've tried letting it sit like that for a while, but it remains locked up. When I restart Sonar, it will open other files just fine. What can I do to fix this?

Thanks.

Thanks! That opened the file. I had Sonar disable all the plugins. Now how do I find out what is causing the problem? I was using this file with all of these plugins for the past two weeks without a problem. How do I go about troubleshooting, or more importantly, prevent it from happening again? I wasn't anywhere near the capacity of the system.

But what would be the reason that the plugin would cause a problem? They were all working fine for the previous two weeks.

I responded a little too early before. I had opened the file but not played it. When I tried to play it, the disk meter shot all the way to the right, and I got a dropout. Previously it had been in the 25% area whenever I played this file. I tried adjusting the buffers in both Sonar and the M-Audio control panel, but nothing helped. I deleted the aud.ini file - no luck. I reinstalled the Delta drivers - no luck. Finally I reinstalled Sonar, applied the 4.0.1 and 4.0.2 updates and it finally worked.

I haven't been able to use 4.0.3 because I get a rythmic clicking in the audio that goes away if I use 4.0.2.

My system is an Asus A8V deluxe, Athlon 64 3000, 2GB RAM, two Delta cards synced together through the SPDIF connection. I had been using this system and software without problems for the last 7 seven months. I only began to have problems when I tried 4.0.3. I used system restore to get back to 4.0.2. I wonder if that screwed something up.

Thanks for your help.