XP clients hang accessing shared 2003 folder

Hello... and thanks in advance for any help!

We have a Server 2003 domain with a dozen or so XP SP2 clients. When 2 or more clients are accessing a mapped folder on the server (e.g. \\server\public\fax\incoming) sooner or later the clients that are accessing the shared folder hang tight. There is no escape! Nothing short of a power off cold start of the hung client machines will get things going again. If only one client is accessing the folder everything is fine, but as soon as two or more clients attempt to access the folder.... within 5 to 30 minutes they lock up. Clients that are not accessing the folder are unaffected.

The "incoming" folder contains about 1 GB of tiff files (faxes). There's nothing special about the folder... the users have normal permissions, no user restrictions, no encryption, no compression.

Any help will be appreciated!!!

Geff