Every few months, Outlook 2003 will get into a situation where it will no longer render images in the preview pane or the message window. If you reply to the message, then you will see the image.
Perplexed by the problem, I would take the brute force "Detect and Repair" solution but that isn't always desirable as it resets all the Outlook settings and takes a while. Months ago, some one posted to an internal DL that the problem can be fixed by deleting the Outlook Temporary Cache folder. Since then I had forgotten this solution, and noticed the problem re-appeared. I was talking to Reeves today and he mentioned that he is having the same problem.
Anyway, here is how you fix the problem.
Problem solved! I could not locate a KB article on this topic.