We're running into a problem with certain files and folders on our Windows 2003 R2 file share. The problem only affects OS X 10.6 clients.
Certain files and folders on the share seem to lose their filetype association. For 10.6 clients, the file or folder becomes greyed out. Older OS X clients (ours here are running 10.4, I don't have a 10.5 machine to test with) and windows machines have no problem.
In addition to becoming greyed out, if it's a folder, the icon displayed in the list view is the generic document icon. (You know, the blank piece of paper with the top-right corner folded down) Quick look and Get info both still indicate the "kind" is folder, but double-clicking the folder does nothing. The folder behaves completely normally in the terminal, only finder has the issue. Renaming, moving, or copying the folder to a local drive does not resolve the issue.