Quote: "I need to know how others are posting images so that I can repost them."
There are various ways. The way that I usually use (I don't claim it's the simplest or best) is that I first attach the image to the post. I then send the post and when the post appears I right click the View button and copy the shortcut. I then edit my post and paste the shortcut. I then select the pasted shortcut text and click the image button. Finally hit the edit message button to post the edited version. The edited message should then contain the images you inserted.
If you have the images on your own web site or other web location then you can bypass the editing step and just insert the links into your original message (using the image tags of course).
The images still need to be available on the original links otherwise they won't show so I guess you got an error because the images had been removed from their original location - or the link was wrong perhaps.