Sounds like you have variant 15:
Variant 15: Mupdate - Turning up everywhere
Approx date first sighted: October 13, 2003
Log reference:
http://forums.spywareinfo.com/index.php?showtopic=13613
Symptoms: Homepage changing to searchv.com, redirections to runsearch when mistyping URLs, *.masspass.com in the Trusted Zone, hijack returning on a reboot.
Cleverness: 9/10
Manual removal difficulty: Involves some Registry editing and lots of ini file editing.
Identifying lines in HijackThis log:
Go to the previously mentioned site and try digesting most of it, the link to download CWShredder is towards the bottomn in the "Epiloge" section.
Gilly