I've heard from multiple sources that Rarity (and only Rarity) seems to reset randomly, causing people to lose all data. Normally this could occur if an addon is updated while the game is running; however, this doesn't appear to be the case here.

The only other explanation I can come up with right now is that the weird profile reset code based on version number, which I don't really understand, is bugged and causes the profile to be reset even though I think I disabled it long ago. The lastRevision entry in the SavedVariables appears to be always 0, which indicates something might be wrong with this code.

Will have to investigate to see if it's a bug in the addon.

I don't see how the code would ever be executed, but I've removed it in 5b7df93 just to be safe.

If this doesn't resolve the problem, it must be something else entirely, but only time will tell.