. . you did your Klez.H check using a DOS based Klez tool after a fresh boot into Safe Mode. I've cleand Klez.H out of dozens of machines who's owners "Update my antivirus almost every day". By time Klez.H fixes were out, much of the world was infected, and updating your antivirus after the fact is futile - Klez.H nails it instantly - it looks like it's running, but it's just spinning of wheels.
I use the Command Software Klez cleaner (but others should work). I copy the compressed file to the hard disk and immediately reboot into Safe Mode, uncompress and run the cleaner immediately. To be quite frank, since May, I've found only one Windows computer that's used to read email that didn't have Klez.H / Elkern.C. MS Office users average about 84 infections, WordPerfect users 33. Top number 340, lowest 16.
The combo of Klez.H and Magistr is particularly annoying, as they protect each other (probably unplanned). I usually have to clean those from a DOS boot with an up-to-date DOS cleaner - and, presuming they haven't cleaned up their "Temporary Internet Files" for six months, it can take hours (no disk cache).
I have had a few cases where Klez.H was cleaned, and an up-to-date antivirus reinstalled after clean, but Klez.H reoccurred. Fortunately these are quite rare.
I'm not saying your problem is Klez.H, just cautioning that it's a tough one to pin down unless you use exactly the right procedure.