Appears to have been a problem with conflicting keyboard shortcuts. I had been using Application Switcher in place of the default Unity switcher. Somehow in the upgrade the keyboard shortcuts got reset, so both were trying to respond to my Alt+Tab.
Disabling Application Switcher prevents the problem. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/989945 Title: rhythmbox causes system to run extremely slowly To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/rhythmbox/+bug/989945/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
