I've had this problem ever since I got Leopard. 10.5.3 has NOT fixed it. Sometimes, at completely random times, SystemUIServer will stop responding. The obvious symptom of this is that the menu bar clock stops refreshing. Oddly, if I go into Terminal, kill SystemUIServer, and restart it, it will run normally, until I close the Terminal window. Then it quits. The only way to get things back to normal that I've found is restarting the computer. Anyone else with this issue?