I see now that "Perform Auto-Type" is what happened to me accidentally. I've never used that feature before, so I didn't know what was going on. It's possible that I have a hardware problem, but no other app, including Keepass 2.58, is showing any strange behavior with the right click (or anything else). I no longer have V2.61 installed, so I can't help with the debugging.
No, I don't have any plugins. And I didn't go from 2.58 to 2.61. I went from 2.61 to 2.58. I don't trust 2.61 anymore. The bug doesn't happen all the time, but it happens pretty often.
right click not working