GUI refresh does not work properly on linux/ubuntu but does on windows

Hello everybody,

I have developed a robotic simulation using swing/awt libraries. Furthermore, I am using the "observer" design pattern (java.util.Observable) so after doing some computations, the graphical components of a JPanel (i.e., the robot, sonar areas, objects, etc.) are refreshed (by invoking repaint method).

The problem is that when I run the simulation on windows (both XP and vista) everything goes well, but when I run this on ubuntu 8.04 the simulation goes slow, I mean, it seems that there is some problem with GUI refreshing so robot in simulation doesn't look like moving continuously but with some delay. I have measured the time interval between each refreshing invocation, but it is almost the same in both operating systems (roughly 16 miliseconds).

Could anybody help me?
Thanks a lot.