I Faced this problem before take care,
1- Try to check this version of Revit is haven't any problems
2- try to close revit if this problem is Appeared and reopen it again immediatly to check this happen while you are working
3- Check the Path of the Keyboard shortcut File to see if it places with the right name and in his place or try to replace a new Keyboard short cut
This Link will help you with this
https://knowledge.autodesk.com/support/revit-products/learn-explore/caas/CloudHelp/cloudhelp/2014/EN...
Best Regards,,
----------------------------------------------------------------------------------
If the above reply answers your question; Please mark it with ACCEPT SOLUTION
----------------------------------------------------------------------------------
Mohamed Nassar , ACP, Autodesk Ambassador Gold
BIM Support / Structure Modeler