Windows 7: File and Folder Sharing Issues

[palindrome]

I rebooted after I installed some Windows Updates and ATI Catalyst 10.1. Now my shared folders cannot be accessed over the network from other computers. No settings were changed, everything in the Network and Sharing Center was verified to be the way I left it. Permissions on the folders include "Everyone" with full write access. I think something went kablooie...

Running Windows 7 x64 Ultimate

I don't even know where to go from here. I've tried disabling the shared folders and resharing them. Changed settings in the network and sharing center to no avail. Suggestions on how to proceed would be appreciated!