it looks like typical explorer sticking - it's independent of ram/speed - but that would affect everything (i know it well, it happened to me again yesterday as a matter of fact). in any event, rebooting fixes it.
you might want to get a cpu monitor if you don't already have one (i use
atm) and take a look at the resources winmx (or something else?) is using. might give you some ideas.
- js.