Iffy network connection

I have a home wired/wireless network with 5 machines (Win 7, Vista and XP)
that have been humming along nicely until recently. My main XP SP3 desktop
(wired) has begun hiccuping when downloading pages from the web. IE tabs
will have the little spinny thing while the page remains blank for minutes
at a time. The status bar might say "Webite found" and/or "waiting for" the
website. Sometimes it will say "Done", but there's nothing on the page. I
can click the reload button repeatedly with seemingly no effect, then wham,
the page will load suddenly and quickly. This happens in IE and Firefix.
Sometimes I get so frustrated that I reboot, which works for a time, then
the problem arises again. I don't know what changed and I don't know what to
check. My Belkin Wireless router has the latest firmware update. No other
machines are experiencing the problem and I can see and access all of them;
just the internet is spotty. Help!