JerEvil,
That's exactly what I did. I deleted everything after backing up my commercial rigs. Once everything was deleted from my computer, I installed the older version of Rig Manager 1.35. I got it working without my Kemper connected. Including the Rig exchange. then I updated to 1.5.13 beta and checked it. It all worked fine. Then I connected to my Kemper and that worked as well. At that point I powered down my Kemper and updated to 1.5.20. I started it without the Kemper connected after rebooting my computer. Made sure everything was good with all of that. Once I confirmed that was working, I connected my Kemper and made sure that was working. I then imported my Favorites and Performances from my Kemper. Then finally I reimported all of my commercial rigs and organized them. Since then everything has worked fine. I think the main things was that it cleared out the Private uploaded rigs from my system with illegal characters. I'm not sure why but it's working now.
One thing I have noticed is that my Kemper will occasionally lock when I'm editing performances through the Rig Manager. It sometimes doesn't put rigs in the correct slot and Rig Manager isn't changing the name of the slot if the slot is already occupied. My work around has been to work on the performance locally in Rig Manager then move it to the Kemper after deleting the old performance from the Kemper. HTH
The places I deleted where:
Applications/Rig Manager
Users/Username/Library/Application Support/Kemper Amps
/Users/Username/Documents/Kemper
Mac HD/Users/Username/Library/Application Support/Kemper
Mac HD/Library/Extensions/KemperProfiler.kext