MSN Messenger 80048820 error

I am having trouble signing into Messenger. I get the above error message,
and I have read and implemented all other recommendations I have found on the
internet.

This only happens when I have Service Pack 2 installed. I removed it and
Messenger worked fine, but I reinstalled it as my computer works better with
it.

I have disabled the Windows Firewall, although when I go into the Security
Center it says Firewall is ON, but I am assuming that this is just
recognising my McAfee firewall. When I go into the Windows firewall it says
it is disabled.

Please help, as not having Messenger is very annoying!