AV also means Anti-Virus which is N/A. The problem probably is the combination of Creative + Marvell.
Oddly, yes in this case, 'my curiosity' -- if you [A] Disable the Creative in the Device Manager and use the onboard sound does that 'fix' the problem? You might also want to try disabling ALL sound but the Creative. In either case followed by a restart.
Try [A] or
If it does fix the lagging then keep it that way until you can Disable the Marvell and Enable the Creative/Onboard. Why drive yourself nuts for a month or probably two.