Existing users, 
You can add me to the list of people who have had problems with 10.4.3.
At first I noticed that the Network menu wasn't updating (it was hung at zero/zero for Tx/Rx). When I moused down on it, nothing happened (I didn't the the drop-down that indicated what the interfaces were doing). Finally, I uncheked the "Display Network Menu Meter" in the preferences, and got a sheet that said, "Menu Extra Could Not Load // For instructions on enabling third-party menu extras please see the documentation."
I've never seen this error message before, and logging out and back in made only a temporary difference (ditto for logging out and back in with shift-key held to suppress Login Items).
I am convinced that this latest version of the OS has broken some aspect of Menu Meters.
MenuMeters
Menu extras: CPU, disk, memory & network monitoring.
Version: 1.4b4
Problems with Mac OS X 10.4.3 ("Me Too")
Feedback Type: Troubleshooting Report
Contributed by: Steve Davidson Sunday, November 20 2005 @ 08:18 AM PST
Product Platform: MacOSX
Used Product For: Over One Year
System Info:Mac OS X 10.4.3
PowerBook G4 (15" Aluminum FW800)
2GB RAM
Comments
Problems with Mac OS X 10.4.3 ("Me Too") - Steve Davidson
I appreciate the suggestion, however I have no other menu modifiers installed (and made no other system changes surrounding my jump from 10.3.9 to 10.4.3).I've got another clue to the puzzle, which I will post in a new item (since comments tend to get buried).
Wednesday, December 21 2005 @ 11:13 AM PST
Problems with Mac OS X 10.4.3 ("Me Too") - Steve Davidson
The History file for the most recent update (v1.3) answers the question: There was an incompatibility with Cisco VPN, which I use for all un-wired networking.I had to update to the current Cisco VPN when I made the jump to Mac OS X 10.4. The changes were simultaneous, and I incorrectly ascribed the conflict as being between MenuMeters and the new Mac OS, when in fact the conflict was between MenuMeters and Cisco VPN.
Saturday, February 11 2006 @ 09:52 AM PST
Problems with Mac OS X 10.4.3 ("Me Too") - nosralmot
If you are getting the "Menu can not load...." dialog box, it likely means that your 3rd party menu extras enabler (e.g., either MenuCracker (free from http://sourceforge.net/projects/menucracker/) or Menu Extra Enabler (free from Unsanity, http://www.unsanity.com/)) has come up missing or been clobbered. See "MenuMeters Read Me.rtf" for a hint that this may be the issue. Reinstalling MenuCracker fixed the "menu can not load ...." problem described here for me on a dual 2.7 G5. Oddly, I have a collection of machines running 10.4.3, 10.3.9, and 10.2.8 and only the one machine experienced the "can't load" issue and this was after an update to 10.4.3 wherein MenuMeters worked without complaint before and for some weeks after the OS update and then broke!Reply to This
Tuesday, December 06 2005 @ 03:19 PM PST