Some users can't see a disk in Windows Explorer

I have a couple of users who Remote Desktop Connect to a Windows Server 2003
Enterprise x64 Edition SP2. When they double-click "My Computer", they do
not see one of the SAN attached disks. However, from a command line, they
can set default to that disk, and create and otherwise manipulate files. The
applications they use, the disk is visible when openning and/or saving files.
Other users, including myself, do see this disk in Windows Explorer!

What can I, or the "problem users", do to make this disk visible in Windows
Explorer??

Thanks,