This has happened twice since I upgraded to 10.4.10, the amount of uptime doesn't seem to be a factor.

I will try to open a new application and the icon will just bounce in the dock for a few minutes. Any already running applications continue to be usable. I have to logout/login or reboot to fix.

While in this condition I can see that /var/log/windowserver.log is growing at about 100MB a minute. If I kill the "WindowServer" processes (which are taking up 100% of the CPU) the activity on the log file stops. This is the repeating entry:
"invalid name: CGXRunOneServerPass: mach_msg (gServiceSet) failed (last RPC: LaunchAppRequestWithAuditInfo)"

There is a repeating entry in dmesg:
"fs_events: add_event: event queue is full! dropping events."

8.10.1 Darwin Kernel Version 8.10.1: Wed May 23 16:33:00 PDT 2007