I have a problem that is remarkably similar to yours and I am running pretty much the same configuration bar the DAW (Ableton live
and a little less ram. Same imac though and I presume (TI2 Kbd) the same Virus!
I am only able to run two tracks off the Virus though, and time and time again it will hang a note or two and then either stop playing audio altogether or crash in a horrible audio mess!! Sometimes a soft reset of the Virus will postpone the issue for an hour, but generally it fails within about 10-15 mins of use.
Seem to have had more issues since moving to OSX 10.6.6 so not sure if this is related, although it did do it a few times before this update.
I know that 10.6.6 introduced a few bugs, one of which being a slow bootup which was spotlight and apple store related, so perhaps there is more to it than meets the eye?!
Unfortunately, I am using the virus less and less for projects these days due to the instability of Virus Control....which is a crying shame considering the price of the thing! Would dearly love to fix this, and hope that a Virus OS update (I believe I am on 4.0) will help, but it seems that with every update I have still got the crashing issue!!!
Spec :
imac core i3 3.06 Ghz
4Gb ram (soon to be 8Gb)
External Lexicon Alpha Audio interface (USB)
Virus TI2 Kbd
Ableton Live 8
Project : 25-30 tracks of mixed audio and VSTi's
Would love to hear from you if you have had any luck in getting your issue solved, or perhaps any feedback at all really on the issue.