From the Apple discussion groups comes this fix, courtesy of Ben Harrison
Apple - Discussions - Fixed Airport Drop Outs:
My G4 tower streamed music with no drop outs my g4 laptop would drop out all the time both using original b airport card. To fix it I went to SystemPrefs>Quicktime>Connection and put it on 112kb/s instead of the 1mb/s (that is my work internet connection speed). No drop outs - none I even sent a 12mb file across the network to another a mac whilst streaming - still no drop outs.
