if you look in the windows event viewer log, it might provide some more info on why mp3gain.exe is failing
Nothing in the event viewer, but I did find a number of mp3gain.exe.xxxx.dmp files in \users\phred\AppData\local\CrashDumps. They're all 4.11mb in size and binary. So NotePad++ can't read them. A quick search online shows that in order to read them I need the Windows Driver Kit, WinDbg, and Visual Studio.
If anyone has these, or has a way to read crash dumps, I'd be happy to upland a .dmp to you for interpretation.
In the meantime, I downloaded the full install of mp3gain which is the same version as currently installed. I uninstalled the old one and reinstalled the new one where it was originally: G:\mp3gain\
Hmmm ... mp3gain.exe in the MB folder is v1.5.0.2. The one I just downloaded & installed in G:\mp3gain\ is/was 1.2.5. Should I try replacing new with old?
Or replacing 1.5.0.2 in the MB folder with 1.2.5? Or with a freshly downloaded 1.5.0.2?
also try adding mp3gain.exe from the musicbee folder to your security software exception list
Once the current test scan is complete, and if it still errors, I'll add it to my AV whitelist.