I'm running the Kubuntu Gutsy Gibbon linux distribution. Randomly, the SHIFT key will stop functioning. It seems to somehow be related to running VMWare Workstation and switching screens. It's a known bug listed here:https://bugs.launchpad.net/ubuntu/+source/linux/+bug/195982
Getting your SHIFT key working again does not require a reboot. Simply enter the command
in a command window and it'll reset it. Update:
Rumor has it that upgrading to VMware 6.5 fixes the problem.