For some strange reason the Measure Units/Precision dialogue box will not let me Use custom settings. Whenever I click this a pop-up appears before I'm able to make any changes and says "Please enter an integer between 2 and 256.". Anyone else run across this? I have used custom settings on the measure tool for years, but now I can't and it feels like i'm gasping for air!
I couldn't tell from your screen shot if this is your problem or not, but I ran into this when my denominator for fractions somehow got set to 0 (not by my doing).
If this is part of your problem, select fractions. Then when the pop-up window says "Please enter an integer between 2 and 256", just hit OK.
It will then have the fractions selected and you can enter 8 or some number for the denominator.
I had to do this in a new document, and then save the corrected file as a template for my problem to go away. So for me it was related to the settings within the template, which got corrupted during a SP update or something.
Rich