XP SP2 and Remote Desktop

OK I have a problem with XP SP2. All my remote desktop sessions have quit working. I’ve tweaked firewall settings on client and server side, making sure the “remote desktop” button was checked. But doesn’t seem to be working. Very bummer. No obvious threads on this problem that I can find on google or msdn — there is some discussion about extra work needed to permit remote desktop sessions as part of netmeeting, but these tips seem to be specific to netmeeting. Hmm.