Several forum members have recently reported problems posting photos to the forum using ImageShack, UpMyPhoto or direct-link methods. Unfortunately, there is nothing much I can do about this, as ForumUp Forums periodically update the forum interface centrally for all of their forums.
ImageShack seems to have worked ok in the past, just keep trying various methods and hopefully some will work. Please let me know in this thread if problems persist and please post a link to the thread in question.