I have looked thru google about 10 different times over the last month and I have had it. Randomly my icons in my user folder vanish (See photo) Also "My Computer" hangs and the icons on the right have little hovering magnifying glasses as if it's searching for them. The only way to fix it is to kill Explorer.exe and restart it. Sometimes it happens 4-5 times a day. I have tried deleting and resetting the thumbnail cache (a couple of times) and run a couple of scans (Virus, comuter, etc). So far I have not been able to figure this out and it's annoying. I'm running Windows 7 if that helps.
Here's a thread I found in a Windows 7 forum. Some of the users were having similar problems to yours. Hopefully this helps: http://www.sevenforums.com/tutorials/49819-icon-cache-rebuild.html