Recipe #497 for how to crash ArcMap hard: select Referenced Mosaic Dataset >> Repair paths >> set new to path\to\R_Master >> wait for completion >> 2x-click on path\to\R_Master. >>>>> BOOM!

Spot my mistake?

In order to avoid making a typo, and to save time, I copied the New Path from the first field -- and forgot to remove R_, making the referenced dataset refer to itself. Doh!

Sigh. 1.5 hours wasted troubleshooting. In my defence I'd like to point out that if we were ALLOWED TO USE RELATIVE PATHS like we used to be able to 25 years ago with ArcInfo/View image catalogues this probably would never have happened, because the mosaics would have just worked when moved to a new server.

Please, go vote for Relative path names for mosaic datasets | GeoNet and Relative path names for mosaic datasets | GeoNet. Thanks.