Looks like the file is missing in the thumbs folder.
http://www.outdoorking.com/forum/gallery/61/thumbs/609.jpg
Even in the medium and full folders.
Possibly it was deleted and a pointer is still there.
Could try rebuilding content to see if it goes away.

Edit
And clear cache using the method Rick suggested

Last edited by Ruben; 05/21/2009 6:09 PM. Reason: Added comment
Blue Man Group
There is no such thing as stupid questions. Just stupid answers