Windows Credential Manager can create weird issues

Just had a weird issue where a user did not get his home folder mapped from the server.
Tried to do a net use * /delete, and run the logon script manually.
This gave a bunch of unknown user and or password.
Finally I found the problem in the Credential Manager, somehow a different username had been made default for the entire fileserver, regardless of the logged on username.
Deleted this credential, and everything worked like a charm again.