TortoiseCVS: FAQ: "Why do the overlay icons sometimes change to random graphics?

The Windows icon cache is a fairly buggy creature. You can solve this in one of the following ways:

* Rebuild the icon cache by using the Rebuild Icons command on the CVS submenu.
* Or increase the icon cache size. Go to HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer and add a new String Value called 'Max Cached Icons'. The default value is 500 - try increasing it to 2048 (see http://support.microsoft.com/support/kb/articles/Q132/6/68.asp for more details).
* Or delete the file called ShellIconCache in your Windows directory. And reboot."