I have a strange issue at a client's office.
I setup a new windows 7 machine to share files. The folder that is being shared will randomly "hide" certain folders to all network users. So network users running XP cannot see certain folders in the share. If a network user were to try to create a folder in the share using the same name as the "hidden" folder, windows tells them that a folder with that name already exists, so the network user's computer can clearly tell that the folder is there, they just can't see it.
I've checked permissions on the folders in question, and they match all the other folders, and the hidden attribute is not checked.