Edit: This has been resolved. Please post here if you can now login or if you still can't. Many thanks.
On the main site (diablo.incgamers.com), I'm shown as logged in, but on diablonut.incgamers.com I see the login box, and I'm unable to comment since I'm not logged in. When I try to log in on DiabloNut, I get the 'Thank you for logging in' page, and it redirects me back to the previous page, but I'm still showing as not logged in.
I've cleared my cookies, but that did not solve it.