@OP: It isn't just you. I also had ICQ go belly up for no real apparent reason. Things have been a bit flakey for with this protocol on the N900 to be honest for some time. I did howevver find that installing Pidgin itself and then using that solved the issue in terms of being able to chat. It's not as nice as having the built in client always on but it works well. Might be a work around for now?