Neil, think out of the box... what was the name of the picture you tried to post.... camera assigned or by you, either one could have been used before by anyone and are in the database. As soon as you get the picture reject stop... hit the back button... copy your post... then rename your picture by adding a 123 or abc or anything else that might make it unique... if you posted 3 pictures there is no way to know which one it is so rename them all, then hit the back button again so you were where you were when you decided to hit reply... now hit reply... paste in your original post, add the pictures and hit post again.
follow that procedure and life gets a little easier.
I have started renaming anything I post so I never see the picture reject message.
Rob... you are one cruel dude