I had the same problem with XMMS, but only when i turned up the volume. I started just keeping the sound low on XMMS and turning up my speakers manually, but you can also go into System, Sound Card Detection, then change the master volume up. Turning up the volume this way seemed to work fine.
Athlon II X2 240 @2.8 GHz
2 GB G.Skill ddr2 pc2-6400
500 GB Western Digital Caviar Blue HDD
40 GB Western Digital HDD