Do you happen to be using native audio on an Intel i810 or 815 motherboard? If so, full duplex audio crashed Linux under OSS, and I think I crashed it the one time I tried it under Alsa too... the solution is to buy a separate soundcard. (I8x0 audio is terrible quality anyway...)
i8x0 -is- a horrible audio card and does cause crashes... unfortunately he's on a laptop so there is little that can be done.
ALSA 0.9 works fine with the i8x0, however... even w/ full duplex.
-andy