Connection blocked?

[Mackem]

Hi,
Been playing online game with my mate when all of a sudden when he tries to connect to my IP he can't. When we went om MSN i couldn't send or receive files from him or my other contacts. I kept getting the message 'internet connection blocked contact your ISP for enabling file downloading' or something along those lines.

Could this just be a temporary connection problem or is there something in my settings somewhere that i've done. I'm not running a firewall or anything btw.

Thanks in advance

Mackem