changing process priorities - permission denied

[slade17]

the gnome system monitor will let me lower the priority of a process. however, it won't let me raise it again is this a bug? all I can do is end the process and restart it, and it will start again with a priority of 0.

for instance, if i lower firefox's priority to 16, then try to raise it again, i get the error:

Cannot change the priority of process with pid 22975 to 15.
Permission denied