Why would I not be able to completely disconnect & connect a mapped drive?

I have a customer who is using WIN2000 server and they have red X’s on their mapped drives. I asked them to go into my computer and to disconnect them so that they would be gone; however, they still remained there on display with red X’s. We even tried to reboot, but there was no change with the conditions of the mapped drives. Is there another way to force the disconnection or do you think this is a permissions related issue?