Ok, my sound card had a buffer setting as well. I use m-audio delta 66.(very high quality card ) it has 4 channels in and out, using balenced 1/4 plugs. i'm using the second set as the control room cue, and first set as mixer board in and transmitter out.
setting the buffer to 768 cured most of the popping on the cue out. air side seems to get priority as it sounds solid even if the cue side pops at lower rate settings below 512. i was albe to lower the sam buffers to 600 ms. cue side still pops sometime when using the pc but air is solid. this seems to be related to this type of card. maybe someone with 2 sound cards can comment about their experence. maybe Xp handles second card priority lower and buffer time differently. I have solved another issue about sound quality but will post that in the preset topic.
mike
97.3 khel FM
http://www.khel973.com