Pandex trojan - Norton and AVG fail to remove it

["Mortimer" <me@xxxxxxxxxxx>]

Has anyone had problems removing the Pandex trojan from a PC which is 
infected? This trojan sends spam via a variety of SMTP servers.

A customer has Norton 360 which successfully identifies that it has found 
Pandex, even during its boot-up checks, and during a virus scan it claims to 
have removed it and needs a reboot to finalise the process. But after the 
boot the thing is still there: you can see Norton trapping some of the 
emails and displaying suitable error messages.

I've scanned in Safe Mode with no networking. I've temporarily installed AVG 
Free and scanned with that in Safe Mode: it claimed to find and disinfect a 
trojan in winlogon.exe. But still the virus is present.

I've also scanned with Spybot 1.6 and removed the threats that it found.

I can't see any rogue programs being started in Start | Programs | Startup 
or HKCU/HKLM | Software | Microsoft | Windows | Current Version | Run.

Any suggestions? The various "How do I remove Pandex" articles found from a 
Google search seem to imply that Norton, AVG, Panda and Kaspersky will find 
and remove Pandex successfully.

It's getting to the stage where a rebuild might be quicker than 
investigating further...