Blank explorer

I have recently set up a small P2P home network using an XP, W2K and an ME
machine. The W2K machine is the internet sharing computer. At one point in
time I had things all working, but for some odd reason while the W2K machine
continues to work just fine, the XP and ME machines both seem to have a
problem displaying an internet page.

What happens is this: I start explorer on either the XP or ME machine and
do something that requires an internet resource - say, MS Update - the W2k
machine dials, the website connects and the explorer claims it's downloading
various items, and finally says it's done. But then it doesn't display
anything. It just sits there with a blank screen.

Any ideas? This one's got me baffled.