I can't see what the pattern is. I wonder if something's happened at a server level, maybe due to an automatical software update, rather than due to a manual reset? I'd suggest we stay here until we hear from Tom, as we'd want to be sure that we have an active administrator sorting out issues as they arise.
But if we can create new posts, the old forum has better facilities for uploads, so we could use the file forum, at least.
Has there been a software update? I notice I can expand each category with a grey drop-down arrow on the right, and there is a 'create poll' button inside each category. I don't remember seeing these before, but I have just cleared out my cache and temp files so maybe these arrived a while back and my PC didn't display them!