Jan,

See if this link helps:
http://dmzweb3.europe.creative.com/SRVS/CGI-BIN/WEBCGI.EXE/,/?St=34,E=0000000000004088782,K=6922,Sxi=1,Case=obj(1091)

This is an official Creative Labs support page, offering advice on "Popping or crackling noises during record or playback with an SB Live!". It contains the main suggestions I remember reading when I was following the soundblaster newsgroup some time ago.

Hope this helps.
Regards,
Mike