OK. This is bizarre. When I use my powerbook to access my desktop's music library and then play that shared music through my airport express, web browsing slows to a crawl on my powerbook. Other internet applications (iChat, Mail, Colloquy) work fine, but web access is incredibly sluggish—if the pages open at all.
If I pause iTunes, the pages load fine. No other computers on the network are affected, and all are either wired directly into the network or use 802.11g.
Any ideas?