Just experienced the not-able-to-use-email problem again. Restarting the PC was the solution. But…after one send-receive action, the problem rises again. I think it has something to do with Norton Internet Security. That’s the only thing that changed recently.
Update: Guess I’m not the only one having problems with NIS2005 and mail: see this discussion.
Update (5/12/2004): The problem was NIS2005. Uninstalling it makes mail run smoothly again. But I don’t want to be surfing unprotected, so I’ll have to look into that a.s.a.p.