Puzzling loss of wireless communication

Equipment as follows:
1) Router is a 802.11b Linksys BEFW11S4 connected to cable modem;
2) Toshiba notebook with internal 802.11b antenna;
3) Win98SE desktop with external 802.11b Linksys WUSB12 USB adapter
located less than three feet from the router.

The notebook has never lost communication with the router. The
desktop has frequent loss of communication. The loss usually occurs
without warning; for example, suddenly the browser won't open the next
page. Pinging 4.2.2.2 gets timeouts, yet the tray icon continues to
show an Excellent (100%) signal. Communication is always restored by
disconnecting the router's power cord for 10 seconds. No desktop
reboots or fiddling with the USB adapter have been required.

I don't understand why momentarily disconnecting power to the router
restores communication with the desktop. It seems to me if the
problem were with the router, the notebook would also lose
communication. Since it is the desktop that always has the problem I
would think the USB adapter (or the machine the adapter is attached
to) is the culprit. It doesn't make sense that the router can somehow
single out the desktop to ignore. By the way, this is the second USB
adapter for the desktop--the first was returned for exchange because
it behaved the same way, and all parties felt it must have been
faulty.

I guess my question is where does the problem most likely lie?
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