Does the problem happened when you try to log-in in the communities? Or when did this happened to you? I just tried it with IE, Firefox and Chrome and worked fine.
Have you did some changes in proxy or your firewall?
What kind of connection do you have (VPN, ..) ? It could be restricting the Intel content.
Go to IE, Tools > Internet Options > Connections > LAN Settings. In there de-select the Use automatic configuration script and select the Automatically detect settings.
The problem only appears with Firefox (so far). I can still communicate with IE without errors.
I have a normal (sortof) home setup. The settings you mentioned I believe are IE specific.
It would not surprise me there is some issue with firefox.
The way I would run into it, is to go to Intel site and log in, maybe doing a few things. Then go away for awhile so the login times out. Now click on something. Before it might take me to the login screen, or some cryptic message, like invalid something, contact system administrator.... Normally after this would click on my top link to go to site and then login again. But last two days, this appears to want to error out, with new message mentioned.
Note: Firefox still has issues with how the security stuff works on your website. I have also had IE complain about something like the security handle is not valid and should I continue anyway (or something like this). Note: I have also have seen issues on IPad, where again if I have a session going on the Intel sites, then go away long enough for Intel to timeout the session, then if I click on some link or like it tries to take you back to login screen, but errors out with some error like, invalid session ID with some number, that says to contact the Intel network administrator... But in this case I simply go back to my bookmark to Intel site and it takes me to proper login screen...
I have also had a couple instances on Intel site, where trying to post something that is part of PM will simply hang there and not post. This just happened again this morning, which you might see in the image:
Note: the (1) indicator was for your posting... Will try again to remember all of the text I was posting to try to get his TFT display to work...