Problem solved, har du rensat lite språk kanske... Fungerade för mig ( från Macfixit ) :
Do you see these messages in install.log?
> Some languages were not installed:
If so, first extract those language resources from SecUpd2007-002Ti.pkg manually, with Pacifist or Terminal commands, and put them into iChat.app, then install the update.
Please be sure to put only those language resources indicated in install.log, so not to overwrite/destroy existing ones. And those for InstantMessage.framework can be untouched.
After the installation, you could delete unneeded language resources.