Update: For anybody else who experiences this issue after updating to 11.04, the fix is to delete the folder ~/.gstreamer-0.10. After doing that, the issue should be fixed immediately without a need to logout or reboot your system. It would appear that the problem was a corrupt gstreamer configuration. Perhaps the error messages could be modified to make this more apparent?
Update: For anybody else who experiences this issue after updating to 11.04, the fix is to delete the folder ~/.gstreamer-0.10. After doing that, the issue should be fixed immediately without a need to logout or reboot your system. It would appear that the problem was a corrupt gstreamer configuration. Perhaps the error messages could be modified to make this more apparent?