I recently experienced horrible crack pops and out of sync problems with my Virus TI2 Polar.
Several causes: I switched OS to Win 7, updated from Ableton 7 to 8, installed new PCI soundcard, updated Virus OS, All around the same time so I didn't know what was causing my newfound and horrible problems.
Sometimes VS would tell me there was an out of sync problem.
This kind of problems totally drove me nuts, and I set to solve it.
First thing I did was installing a new PCI USB card in my computer, and used it dedicated for the Virus. That didn't help, so I also switched the physical location of the USB card to a different PCI slot. Also that didn't help.
To test whether the problems were caused by other USB equipment attached to my computer. I removed all of them (including my keyboard and mouse), still the problems occured.
I read something about the internal PCI/USB whatever transfer speed is the bottleneck, so I disabled my PCI soundcard in the hardware control panel. Althought it didnt seem to be necessary, as I was not using my soundcared. It did solve my problems to a large extent. No more out of sync and lag problems. However, now and then some cracks, but then again i'm using some wild patches :).
I'm interested in reading other people's experience about this matter. To be honost, I was quite d