Revit 2012 - Ribbon behavior due to .Net 4.5 installation

Hotfix - Autodesk Revit 2012 - Ribbon behavior due to .Net 4.5 installation

This hotfix corrects the behavior of the ribbon panels after .Net 4.5 is installed.

Make sure that Update Release 2 has been applied prior to adding the hotfix. Verify that the build number of Revit 2012 is 20110916_2132. If the build number is 20120126_0600, it indicates that Update Release 2 and the Memory Allocator Hotfix has been applied.

The Readme contains the latest information regarding the installation and use of this update. It is strongly recommended that you read the entire document before you apply the update to your product. For your reference, you should save the Readme to your hard drive or print a copy.

Link: 
http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=21344242&linkID=9273944


Source: Autodesk site