If Explorer is shown a directory with some corrupt AVI or JPEG than it will lock up and you see your issue. Microsoft has not provided a fix for this one yet.

The other repeatable was related to what I noted and Nero Scout. To fix that I had to uninstall Nero Scout since Nero would have to re-do their code to not rely on MSFT for a fix.

These are two with causes and no fix. More about malware causes at http://forums.cnet.com/5208-6122_102-0.html?threadID=328220#2968150
Bob