Well, it seems the discussion confirms this bug anyway, but since I just experienced it as well, I'll add my vote. brltty grabs the connection and removes the raw serial device, and so obviously removing brltty fixed it.
** Changed in: brltty (Ubuntu) Status: Unconfirmed => Confirmed -- Arduino detected as braille device https://launchpad.net/bugs/84139 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs