I got my roommate into d20Pro, as he wanted a laptop to control his own character's movement for our face-to-face games. He upgraded to the (at the time) latest version. Our clients couldn't communicate, using different versions. I tried upgrading my client a while back, on both the desktop and the laptop. No issues as far as upgrading went... but my (older) desktop then ran d20Pro so slowly I could not do campaign preparation on it. Original version 3.7.3 (64-bit). Attempted upgrade version 3.7.6 (64-bit). The laptop could run either smoothly. I attempted to downgrade to my original version. Uninstaller, and then removed the Mesa Mundi folder. Then reinstalled from my saved 3.7.3 file. I get an Import Legacy Content window. I click okay. That prompts an Error popup window. Failed to addStored Feature Behavior. You files appear to be corrupt or from a prior version. Please delete your dm/stored/feature directory and restart. *Caused by: Failed to addStored Feature Behavior. Your files appear to be corrupt or from a prior version. Please delete your dm/stored/feature directory and restart. Deleting the folder, I get the same thing, on every restart. Clicking OK gets the error (even if the folder is removed) If I click Cancel, then the older version runs mostly fine. The visible ring/glow/light radius works as per the new version, even though the desired 3.7.3 version has been installed. I even edited the registry, on the most recent delete. And removed every last entry that mentioned d20Pro or Mesamundi. On reinstall, I obviously missed something... as it knew my username, although it prompted me to register. And the same error box, on Import Legacy Content.