It happens here and there. Most likely not a TripleA issue, but the webserver responding.
You also get this message when you are trying to send more than one posting during 15 sec using your browser.
I believe inline pic posting is disabled, but if you click on the button of the picture (2nd row, 2nd button), then fill in the URL of your pic, it may show up.
Otherwise, you have to click on the additional options link below the message field and attach the file.