Well I tired again and failed. I've decided that it's the router than just can't cope captain. Grrr. Much annoying. I've tried loads of stuff and have infact wasted a whole day in trying to fix it.
Well at least I'm not the only one, I've found a guy on usenet doing a Google groups search who seems to have a similar setup and it's happening to him too. Unfortunatly it doesn't say how he fixed it. I suppose I might email him and see if he solved it. I can see the response being "Yeah, I got a new router". Grrr.