[The Real Slim Shady]

I suspect someone has managed to poison your dns cache.

Why not configure your dns to use opendns like 8.8.8.8 and 8.8.4.4 and see if that solves your problem.

Also, it could be related to your IP address. Up until very recently it was an "unallocated" range by IANA so there is a good chance that the IP is still on old bogon lists (ban lists), which can cause dns and misconfiguration errors. But i doubt that facebook would be using cpanel. Still, a possibility it is.