Linksys wireless probs

Hi, I have a linksys 2.4 broadband wireless router...its hooked up to
a mac laptop (wireless) and also hooked up to the router is a winxp
system, via a cat5 cable...both go to a cable modem.

I have frequent disconnects (maybe once an hour or so) with both
systems, requiring me to have to physically unplug the power cord on
the router then plug it back in....after which it runs fine till the
next time it stops working.

Also, when dl'ing binaries from newsgroups, I get frequent
disconnects, I can;t seem to dl anything of any large size...This
happens only on the cat5 winxp system.
Also, I can't stream audio at all without the disconnects
...
If I hook up the winxp system direct to the modem all works fine and
dandy...
Anyone have any ideas on whats causing this problem??
Many thanks!
Chris