wordpress site loading issues

i have multiple sites on my webserver out of all of them, ONE is php and cannot load from the outside of my network, however while on the same network as the webserver it loads just fine, the other html sites load with no problem what so ever. i have done the following for troubleshooting:

as wordpress 3.04 i disabled all plugins – didnt work
upgraded to a faster machine – didnt work
upgraded wordpress 3.1 – didnt work
removed and re installed plugins – didnt work

i tried doing a ping -a to my wordpress blog and it times out
also did an nslookup and didnt get positive results either

i am currently using dot.tk for website names, everything ends in tk

this is a server that i am managing myself

i believe it is a DNS issue but im not sure the steps to go about fixing it

i hope i gave plenty of information

thank you in advance
paul