I was having similar issues last night.
I can sign in now, but for many forums I have to sign directly in eg. for QF I need to just type
www.flyert into the URL field in the browser and select the one in the dropdown list that ends in 498 (for QF). Then, if I click the link near the top for 'airline programs', I get taken to Miles and Points, with some threads directly accessible and other 'grouped' ones (eg. airline programs, airline alliances) with the blue background, refusing to 'work' or do anything when clicked upon.
Weird. And this happened earlier today at work, and is happening now at home (signed in, and not signed in)
So I can visit the forums (fora?) I normally do, it just takes extra time doing it the long way (I don't recall the suffix number for most of them so I have to go one by one).
Is anyone else experiencing this? I'll lodge a 'call' with tech support if it is still happening in a day or two (but cannot believe I'm the only person this is happening to).