I moved the website to a new dedicated server over a month ago. I installed ImageMagick and all seemed to be working, but we never tested uploading to one of the categories with watermarking enabled.
How do I tell if my PNG library is bad? When I run composite from command line, it displays the help text, so I assume its working. The watermark.png file is not corrupt. Here's a link to it:
http://www.memphisracingscene.com/pp/watermark.png