Still no luck with this problem. No useful response at Ubuntu Forums, but I have found this bug report
I have confirmed the problem is that my system continuously connects and disconnects rather than fails to detect the BB.
I tried loading the uhci module described by Rivviepop but that did not work. Ditto the fixes discussed in the bug report. I have not been able to make any other workaround. If I do find a solution, I'll post here.