I have also been unable to upload attachments for at least the last hour. (I last sucessfully uploaded a JPG on 10/26, but haven't tried since.)
Tonight, I tried PDF, PNG, and JPG with no luck. All were within the board's limits in file size, pixels, etc. In the process of trying, I cleared all my previous attachments in case I was over a total storage limit, but that didn't make a difference either.
I can, however, still link pics using the [ img ] tags without a problem.