A quick check on google:
"IPB does not allow images to be grabbed dynamically rather than directly.
Good - - - www.nowhere.com/image.jpg
Bad - - - www.nowhere.com/index.aspx?image=image"
Are you putting the direct image location in the [IMG] tags?
e.g for my sig I had to put:http://i29.photobucket.com/albums/c265/RED_NED/Sig.jpg
With [IMG] tags obviously.
Hope that helps!