Installing Windows 2000 SP4 disables internet connection

Archived from groups: microsoft.public.win2000.general (More info?)

I have just installed Windows 2000 SP 4 (previously on SP2). Now every time I
attempt to connect to the internet I get:
"Dialing attempt 1
Dialing...
Connected to remote computer
Verifying user name and password...
Failed to connect to remote computer
Unable to establish a connection"

This happens for two ISPs so the problem is at my end. Another PC we have
can connect ok using the same ISP settings so it's not the ISP or the
phoneline, it's definitely SP4 that's caused this. I have uninstalled and
reinstalled the modem driver to no effect.

I can't find any previous posts that mention this problem. Any ideas please?

Geoff