From a message in a different forum:
rsirian1
Be careful. If you upload the pictures and hit Send before they finish uploading the post won't have pictures but you won't know about it unless you check your post. I think this happens a lot judging by the number of posts like this one.
If this is the actual problem, could the software detect the condition and prevent the error? Force the user to wait until the upload is competed or cancelled before allowing Send.