Hi Ove.I,
There is a solution without re-installing Autodesk Inventor. Please follow these steps;
1. Please, Go to Windows Start Panel and search for Regedit then open it

2. Please, Go to HKEY_CURRENT_USER folder and open it

3.Please, Go to AUTODESK folder and open it

4.Please, Go to Inventor folder and delete it

5. Please, Then close Regedit and open Inventor finally try Measure command.
It should work.

By the way, please don't move, delete or do any other operation on other folder at the out of HKEY_CURRENT_USER.
I hope these helps.
Thanks
Regards,
Timucin
Timucin E. Tasdemir
Technical Sales Specialist, Turkey
Design and Manufacturing
Autodesk, Inc.