On a machine that it's working type (lets pretend it's flyertalk)
ping flyertalk.com
it will come back and say
Pinging flyertalk.com [98.158.194.68] with 32 bytes of data
If you can use the 98.158.194.68 (just put it in the address) to get to flyertalk (again I fully realize you are not trying to get to flyertalk

) when you call them you can tell them it works just fine by IP address, but not through DNS.