Volume cut problems with X2 on audio tracks, anyone else?

All of a sudden it will just happen out of nowhere, the volume will diminish like about 75% on all my audio tracks (midi and synth tracks seem to be ok).
Has anyone else had this happen to them in X2 as it's never happened until now? I've tried everything to fix it to no avail. It's such a problem that i literally can't even go into my studio to record or edit - it's pretty bad when a man can't even do that :) :(

Tim

Sorry, i always ask that too when i'm trying to help someone out; can't believe i didn't remember to mention it myself. 
I haven't actually tested it out loading up other projects, which i will do, but still, it never did it in X1 or previous versions. 
Also, about half of my wav tracks don't have envelopes on them. That's ok isn't it??

I'm using a Mackie Blackbird interface with Win7 and Sonar (all 64bit) with the onboard Gigabyte Texas Instruments firewire chip.  
I keep Win7 updated regularly.  I really believe it's a Sonar thing (since all previous versions have performed flawlessly on the SAME 
system i'm presently using), but you never know.

It might help.  Let me go see and i'll report back.  Thanks so far!