Sound card cuts in and out constantly?

[Supermercado]

I have two soundcards, the onboard one and an old Soundblaster Live. I use them both; the SBLive for connecting my headset with the microphone and the onboard for game audio, Winamp, etc. (yeah, it's kind of backwards, but it works and it sounds okay, so I don't worry about it). Anyway, I started noticing it last night: every little while, Winamp would stop playing and I'd have no sound. What was really strange was that Winamp would actually stop playing the song - I wouldn't just lose the sound. It started happening again tonight with much more regularity. I tried to play BF2 with my friend and it was doing it there, too. I made sure my speakers aren't causing the problem by testing them with my laptop. It's just regular sounds; Winamp, AIM, games, etc. that aren't working. Even stranger is the fact that it fixed itself when I restarted, but it also fixed itself when I quit BF2 and tried playing a song. It seems so random.

Anyone have any ideas at all for things I could try? I haven't done anything to the computer except some Windows Updates in quite a while.