So, you may or may not remember that I was afflicted with this pain in the neck of a problem: namely, you launch iChat, it loads for a second, and then dies immediately. In trying to solve it, I funted my computer, and needed to reinstall.

Last night, my computer ran out of battery (at the 51% mark, no less – let’s hope this battery holds out), and didn’t sleep, so I gave it a hard reset and thought nothing more.

This morning, I realise I haven’t relaunched iChat – so I do – and it dies immediately. “Bugger,” I think, “this is the same problem as before”. It’s also the same problem my girlfriend’s iBook has.

Then, thanks to this helpful Apple Discussions post, I solved it. The issue is between the iChat in 10.4.3 and my Netgear DG834 wireless router – namely, the implentation of UPnP (Universal Plug n Play) in the Netgear box. My router, incidentally, is on firmware 3.0.something – the latest.

To get iChat working again: log into the router, scroll down the left hand menu and choose the UPnP menu. Then: untick the “enable UPnP” box, click Apply; re-enable it, click Apply.

iChat now works. Bizarre, but fortunately solved. It’s also apparently fixed in 10.4.4, released yesterday, but I’m not upgrading just yet due to being bitten on 10.4.3.