When I updated to 10.4.3 last night, I rebooted and my Antenna, Volume, Input Menu, and Account Menu wouldn't come up in the upper right hand corner of the screen in the menu bar. I checked out the Activity Monitor and the SystemUIServer process was just hanging there -- it was highlighted in red, indicating that the process had stalled.
In the past, I had tried to disable the spotlight menu by renaming the Search.bundle file in /System -> Library -> CoreServices to Search_SAFE.bundle, as suggested in this hint. When I updated the OS, it installed a new Search.bundle, which was apparently causing the hang-up.
To fix the problem, just trash the new Search.bundle (or rename it), and restart the SystemUIServer.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2005110218212563