I used to have the same issue, so I went to Photobucket.com (which is FREE to join) and downloaded the pics from my computer to Photobucket and then copied the "IMG Code" from Photobucket and then transferred them to Singletracks forum. Works great now! Try it , and it should work for you if that is the issue you are having.
I appreciate the knowledge. I just posted some pics and they came out great. Thanks.