Comment 15 for bug 453898

It happens with the -generic kernel too, but if you haven't modified /etc/security/limits.conf your regular user account won't be allowed to chrt anything. Try "sudo chrt 50 totem" to reproduce the problem without changing those settings.

Side note: chrt-ing applications is a common thing to do for semi-pro audio applications, which is mostly what you want UbuntuStudio for. Perhaps the UbuntuStudio maintainers should be subscribed to this bug?