I had some trouble at first with the uploading procedure for photos. Next time try the steps below to see if it helps:

1) Click "Go Advanced"
2) New drop down box, click "add files"
3) Choose file from location on your PC, then "open" and "upload" and then select the uploaded file to place in "attachments" which is the lower half of the last dropdown box. After that click "done" and you should be able to post the reply (you can also choose a preview I believe)

Good Luck,
Dave