Interesting idea, reflashing and not restoring from backup. Question is: What gets restored about the keyboard? Perhaps I can just go into the system and mess with those configuration files.

Incidentally, I tried editing /etc/bluetooth/hcid.conf. There's a config item there that controls the way the Security Manager is used. Normal mode is "user". I tried setting that to "none", which the comments seem to indicate turn off security checking for bluetooth connection. The result was that my keyboard was never found in scanning.

I hope you guys can tell that this is going from an annoying bug to an interesting technical problem!