As of today, at least for the past 9 hours or so, I've been unable to successfully log in to my Battle.net account on both the WoW and Diablo III forums - only the SC2 forums are working. Both WoW and D3 present a "An error has occurred. Please try again." message, preventing me from making a post, though I am still able to access my account successfully through both websites.
The issue persists across three different browses will full cache clears in between. IE10 preview, Opera 11 and whatever version of Chrome they're up to now (it changes every 30 seconds, so I can't tell anymore).