How could an anti-virus, or something preventing writing to the registry explain the "slow creep" to 0? You would expect the setting to not get applied (not stick).
Definitely a weird one.
It's definitely strange. This "creep back down to zero" happens for one band or for many bands at once. Whatever isn't set at zero creeps down until it's all zeroed out.
Mwilliems: I checked the DSP field for a bunch of songs, including several we were testing with and found no values in any of the DSP fields, per song.
I'm pretty sure that the OP (Jim) is running his PC as a non-administrator because when he reinstalled MC, he right clicked and chose "run as administrator".
Another detail that I found strange: I was unable to locate C:\Users\<his username>\AppData . This folder did not seem to exist at all. So I couldn't locate where MC was storing it's library files. I wanted to do this so I could be sure that we deleted the library, including all settings, before reinstalling.
Further, when I went looking for MC database backups, I found some, but only 3 files. One from today and two from February. That's it. In my experience MC makes database backups every 2 to 5 days, and keeps monthly backups seemingly forever. The OP (Jim) said he uses MC constantly, so MC should have been making backups.
The whole thing is really weird and would seem to have some common cause. But I have no idea what that cause might be.
Brian.