I have been plagued by this same "about:blank" hijack that keeps reinstalling itself and things like HJT, CWShreeding, Spybot and Adware Away do not do any good to resolve the problem. Every thim I have rebooted the settings have been restored and each new browser version has opened to the "Search For..." page.
Finally one thing I did has now removed this hijack for two days, with no sign of it returning.
I removed the Google search toolbar from my browser.
I believe this hijack reinstalls itself from software added to the Google toolbar that is re-initiated each time you start your browser after a reboot.
Simply first remove the Google toolbar and then follow other steps through HJT, etc to remove the other entries,etc. You may need to run these in Safe Mode.
Does ANYONE who has this browser hijack NOT have the Google search toolbar? I would be interested to see replies to this.