I think the hijack is disabling the ability to return to normal.
If you do not have "Spybot" (a removal tool for such internet leeches) please download it here: Spybot download
After it is installed run it in advanced mode and go to "tools".
Then you will see an option called "Browser pages".
See if you can see the hijacked serach page there.
If so use the "change" button.
Hopefully you will be able to rin yourself of this pest without having to manually edit registry keys.