@Mike I just started running into a similar issue, from one of my users:
"When I sign on via Explorer 11, I'm shown as signed-in, but I cannot post, and when I move to another page, my signed-in status disappears. But, when I log on via Chrome browser, there is no problem."
"The other day my Internet Explorer updated to IE 11. I wasn't able to stop it from updating. From then on I can't post on the forums. It won't let me type anything into the text box. Is it something with the browser or did I do something wrong and am unable to post?"
Okay, my wife pointed out a third report from yesterday, I'm wondering if it's an addon or something:
"For some reason on my laptop I cannot fill in the message body of my post. It will not let me type anything. It also extends to private messages, but only is affected on my laptop because I'm using my phone for this message. Apparently it was my Internet Explorer. I switched to Google Chrome."