I know that I'm not helping, but my KT, jailbreaked, with only Launcher and usbnetwork installed, didn't updated too.
It raised "Error: 06" when I tried.
My previous (and current) firmware is 5.0.4
UPDATE: It worked! Uninstall all the packages, then uninstall jailbreak, and try again ;-)
Last edited by zamana; 04-12-2012 at 01:05 AM.
Reason: Solution found