Lots of things happened in 2010. The Dems didn't lose the House because of fear about all 3 houses being in D's hands.
http://en.wikipedia....ions,_2010#Issues
Bottom line: Voters were still upset about the economy imploding. Unemployment was too high and they wanted change. They believed the lies that the Republicans were throwing about ("jobs, jobs, jobs", "repeal and replace", etc.). In 2012 they weren't quite as receptive to those lies.
HTH.
Cheers,
Scott.