I have the same problem on a fresh Archlinux installation.
My resolv.conf contains only
(plus a few comments)
It's the address of my "box" (router, modem...). It works perfectly for every other domain (Belgacom is my ISP).
I tried a ping but it fails. I installed Chromium to test and it's working but it's not working with Epiphany, so I guess it's not a problem with Firefox. Other computers (on Ubuntu) using the same address as nameserver can access to this domain.
A dig gives me this result :
; <<>> DiG 9.9.1-P1 <<>> belgacom.be
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 17483
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4000
;; QUESTION SECTION:
;belgacom.be. IN A
;; ANSWER SECTION:
belgacom.be. 1643 IN A 126.96.36.199
;; Query time: 67 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Mon Jul 23 02:57:59 2012
;; MSG SIZE rcvd: 56
I fixed this problem by adding 2 old dns servers to /etc/resolv.conf :