I'm working on a localhost site (developing a theme). Saw Bad Behavior needed an upgrade today, so I upgraded it. Immediately, my widgets started acting funny - I'd fill out a new widget and it would refuse to save; and when I'd try to delete it, it wouldn't delete. So I logged out, shut down the computer (you know "Did you try turning it off and back on again?" ;)) pulled up localhost again and logged in. I was on the dashboard, clicked to go back to the widgets - and was immediately booted out and given a 403 error. The error message (code 7f00-0001-cd36-1abb was given) said I was "trying to log in from a form not associated with this site."
I removed Bad Behavior. I actually remember this happening once before, many moons ago and I recall you all got it sorted out - it's been a long time since this happened. I'm guess some sort of the same bug got popped in the update, so I figured I'd drop in a note and let you know it was happening again.
For now, BB is removed so I can actually log into the site, but figured you should know (and hopefully fix, because I've used BB for *years* and I don't want to stop now!) If you need any other server info or logs or whatever, let me know. I'm on localhost, so I don't mind messing around if it'll help you fix it. :)