For some reason, after installing a program like Icon Packager (a popular program to change your Windows icons), Photoshop v9.0 won't show any kind of thumbnails in the browsing window. This is very odd! But, i only remember it happening with v9.0. Look below:
Has anyone else here encountered that problem?
More aboutproblems photoshop icons
I would check both software's websites in troubleshooting sections on this one.