[bpostal]

So your mic cuts in and out but the mic on your webcam doesn't? Or are you saying that the mic on your webcam cuts in and out in PS2 but not when you've just got the webcam open on it's own?
I'd suggest checking your push to talk settings vs your keybindings in PS2 (on the off chance that a keybinding got mixed up that would make you toggle your PTT on and off)

Barring that, Maybe try a $10 headset from Walmart (if that doesn't fix the problem you can always just return them) to see if the problem is with the mic/webcam exclusively.