Maybe this is helpful for the software engineers.
System:
Macbook. 3.06Ghz Core 2 Duo (4GB DDR3) OS X Lion 10.7.1
Virus TI Keyboard (1st gen) 4.5.1.15 (used as audio and midi interface)
Live 8.2.6 (i.e. latest software)
M3M (no keyboard) 2.0.4 - latest software and hardware upgrades
I usually use Virus as my midi input - and as the soundcard.
I often load the M3 software for trad sounds such as pianos which I can then play with the virus keyboard.
Noticed lots of glitches, small pops etc with minimal system load (e.g. no clips loaded - just m3 software as the only midi instrument - 5% CPU usage in corner) just playing piano or clav via keyboard.
This is before the virus software is launched from live and the system is just being used as a soundcard.
Interestingly when the virus software is loaded as a midi instrument in a new track, the artifacts stop/are massively reduced.
If I then delete the midi track with virus control back in it, then the artifacts restart.
Obviously I can work around this by always including a virus control in a session, although I don't think this is how you intend it to work; I've had no problem using it just as a soundcard for a long time.
Cheers, Domc