SQL Server Management Studio generates error, can't start
Instead of running repair, completely uninstall the client tools using setup, and then reinstall them from scratch. Make sure you also uninstall any add-ins or plug-ins that you're currently using in SSMS. Once you've installed SSMS from the media, then apply SQL Server 2008 R2 Service Pack 1. If you have Visual Studio 2010 also installed on your machine, make sure you've installed service pack 1 there before re-installing client tools.

FWIW, I've found the new features and enhancements in SQL Server 2012's version of Management Studio to be very beneficial, and have been using it as my only SSMS version since the early betas to manage 2005, 2008, 2008 R2 and 2012 instances with no problems. RC0 is out so it may be worth trying that version too. It's a big download for just the client tools, but worth it IMHO. You can get it here:

http://www.microsoft.com/download/en/details.aspx?id=28145