Try this, go to
http://www.dnsstuff.com/
First, under "DNS Lookup" type in "forum.portraitartist.com", or any site you can't access. It will give you the IP number for it.
Then, under "Ping" enter that IP number. Hopefully it will return with some times that it took a sample packet of data to reach that destination.
Then, under "Tracert" enter that IP number. If Pinging worked, this will return with the route that packet of data took to get to its destination. If the packet of data doesn't make it, the last entry in the table is likely where the data got hosed.
Then enter that last IP address in the "IPWHOISLookup", and it will give you some info on who owns the server where the data got lost.
Hope that leads you somewhere!