This is a common issue this week. This issue occurred if you installed Revit 2014 on your computer, but still have Revit 2012 or 2013 installed. After finished installing Revit 2014, you will find that Revit 2012 and 2013 ribbon are messed up. This issue is similar with Revit 2013 installation on Windows 8.
The problem is because Revit 2014 will install .NET Framework 4.5. as prerequisite. This is the one that cause above problem.
There are several hotfix and updates released by Autodesk to fix it. Follow the links below -based on your product- to download updates. Remember, Revit 2013 is the download link if you have Building Design Suite.