Sorry, I don’t know the solution.
Why don’t you ask to Waldo, whocares and/or raman.
Maybe on Google you can find ohter Browser Hijack Killers than you mentioned here. I don’t know much other applications, or better, I don’t know better applications than Spybot, Ad-Aware and HijackThis.
I thought SpywareGuard (resident) and SpywareBlaster could done that job, i.e., prevent the infection ::).