I just had this same problem and the same error message as the one you linked from the other thread.  Could get to the forum but when I clicked a link to a thread I got the error message.  Happened on my PC and my Android phone.  But everything worked OK at work.  So last night, I turned off WiFi on my phone and used data to access the site and it worked.  This told me it was my router or modem (I have separate devices).  I was first thinking I needed to a new IP lease from my ISP but when I logged into my router I noticed there was a firmware update.  I went ahead and updated the firmware which required a reboot of the router.  After that, everything was good.  Not sure if it was the firmware update or just restarting the router, but I'm back in business at home.

Mine seemed to start when I tried to insert a pic from Flickr to a post.  I've used Photobucket in the past but that site has turned into junk and I tried something new.  I got the error message at work right after trying to post the pic from Flickr so thought that was the problem.  Maybe not.  But access to the site cleared up at work; maybe we get new IP's frequently here with our DHCP settings compared to home and my ISP.  At home, I was locked out for a couple days until I did the above.

Maybe try rebooting your modem/router.  Didn't read every word in the thread; maybe you already did this.  If that doesn't do it, maybe roll back the firmware and then renew it to the most recent version.