Its a trojan virus/malware. I had the problem for a week, and research into a number of forums has revealed that many are going through the same thing.
For whatever reason, AVG didn't pick it up and my system was infected. HitMan Pro got rid of some of it, but not all...and the redirect continued. In reading the forum at BleepingComputer.com, it seemed that the effort to rid my system of this would be as much work if not more than just starting over.
I'm fairly good at backing up my files, so my solution was to wipe my hard drive clean and re-install my operating system. Did that yesterday and switched to Norton 360 which appears to be a bit stronger in the detection/prevention of these browser hijacks. I'm just now finishing the restoration of all my files. So far, haven't lost a thing.
Be very careful what you do on-line with a browser hijack attack going on. I avoided all visits to my bank and other sensitive sites until I knew my system was clean.