are you behind a router? if so are the ports forwarded correctly?
check as sometimes if you have not set a static IP Address on your computer then your computers LAN IP Address may have changed, which would make the port forwarding suddenly seem to stop working (it is working, just pointing at what is now the wrong IP Address) that is the most common cause for a problem like that so is always best to check first, if that is not the case then let us know...
