Start menu icons are empty after booting.

When I start my machine or reboot it and right-click on any application in the Start Menu, the icons of the documents/files for that application are blank. But if I close the Start Menu, reopen it, and then right-click again, they're all there. I've tried rebuilding the icon cache but to no avail, and I really don't have any idea where what to do next.

This is what it looks like before the first right click:

This is what it looks like after a right click:

This occurs for any application in the Start Menu (MS Word, Adobe Reader, etc). Which files have and do not have associated icons is random.

Ideas are welcome.