I’m finding a nasty little memory hogging trojan / worm thingy related to the Sasser worm on a few of the machines in my office. See this page for some info on how to get rid of it. Check your task manager. If you see AVSERVER2.EXE running, you should nuke it. If you can’t get rid of it manually, you can use PSKILL from SysInternals to forcefully kill the process.