Welcome to the Autodesk peer support forum!
As for your error, I would suspect it is caused by a problem in your .NET Framework subsystem. You might try reinstalling the latest version of .NET Framework. Keep in mind that 2012 is not compatible with Windows 8, so hopefully you are on a supported system.
It is possible that it needs reinstalled.
.NET Framework issues can be resolved using the .NET Framework Cleanup Tool. More information about this tool can be found at my discussion thread here:
You need to reinstall .NET Framework. You should download and install the full redistributable from Microsoft's website. Then you *might* have to do a repair install of AutoCAD.