Error: Package ‘Microsoft SQL Server Management Studio Package’ failed to load

I have SQL Server 2008 R2 64bit installed with SQL Server Management Studio (SSMS). I've been using SSMS for log time but recently when I try to open the SSMS I get the above error and I am unable to use the SSMS. I've tried all the suggested solutions from this post and this one but I still get the same error. After I delete the registry key suggested by the above articles and re-start the SSMS, I get the following message: "Microsoft SQL Server management studio is configuring the environment for first time use". After a few minutes the message disappears and SSMS closes. When I try to re-open the SSMS (even as Admin) I get the same message (shown above in the title). The users Tony and Chris of online post 2 above have the same exact problem.