I had this problem once before and found the fix to be turning down the hardware acceleration to BASIC in Sounds & MM settings > Audio > Advanced > Performance section in the control panel. Strange but since getting SB LIVE! Platinum 5.1 I did not have to do this but on previous SB LIVE! I found it necessary. Give it a try as it may helped and I really noticed no difference in the sounds so I left it that way all the time, of course others may notice a diff that I did not.
Frank...