Cannot resolve forum.xda-developers.com

I have this really odd issue with my Z3 in that I cannot, on any network (wireless or carrier), resolve through DNS forum.xda-developers.com. I first noticed it because my XDA premium HD app couldn't connect to the forums at all. I did a bit of digging and managed to uncover that I can't connect to anything related to the forums. I CAN however connect to the main portal on www.xda-developers.com.

What I have tried:
1. Different wireless networks - no luck.
2. Other devices - all work fine on all the tried networks.
3. Carrier network (Rogers CA) - no luck, but again with other devices no problem
4. Ping and nslookup through Fing network tools - not able to resolve
5. Ping and nslookup through terminal emulator - not able to resolve
6. hosts file just has the standard localhost entry
7. Browse with Chrome just gives the standard error for unresolvable DNS
8. So far I have only seen this happen on the forums.xda-developers.com address.

I am running a Z3 (D6603) with a custom ROM per below.
Pre-rooted ROM from this thread: http://forum.xda-developers.com/z3/g...0-690-t3056361
D6603_23.4.A.0.546_Customized_US_SuperSU_XZDR2.8.2 1 thanx to @julianbl

It's an odd one for sure, so if anyone has any creative ideas for me to test out please let me know. Thanks in advance.