FWIW....I JUST got thru this same problem last week. Mine ended up being a McAfee SpamKiller app taking up 99% CPU usage. The file was MSKSrvr.exe, which it doesn't look like you have though. Found all sorts of people complaining of the same thing (very sluggish performance) on a McAfee bbs. I uninstalled it and it's like a new computer again.

How's your CPU usage percentage?