0x80042108

We had an XP machine connected to our Exchange 2003 server and checking 3
POP3 mailboxes. This all worked fine but at some point it refused to check
the POP3 mailboxes with this error.

The user can check the POP accounts by logging onto a 2000 with the same
profile so its not the account settings. The XP machine has all the hotfixes
but not SP2. The user has another XP machine with exactly the same problem.
The antivirus has been completely removed. The windows firewall is disabled.
The network settings have been triple checked and are identical to working
PCs. The dns buffer has been flushed. The tcp/ip has been reset.

It has also been noticed that the user cannot ftp through internet explorer
although he can browse to regular websites with no problem.

The user gets the same error when checking the mailboxes individually.

Internet routing is via a BT supplied router although it works fine through
the same router on a 2000 PC.

I have a worrying feeling that's one of the XP hotfixes.