Try changing the size of your icon cache :-
HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/CurrentVersion/Explorer. In the right pane, look for the value named Max Cached Icons.
If the value exists, it's probably set to 500, which is the default value for the key. To change the value, double-click it. You'll then see the Edit String screen. Enter a value of 2000 in the Value Data field and click OK.
If the value doesn't exist, you'll need to add it. Select New | String Value from the Edit menu. The new value will appear in the right pane, prompting you for a value name. Type Max Cached Icons and press [Enter]. Make sure you separate each word with a space. The proper value is Max Cached Icons, not MaxCachedIcons.
Post if this works for you.