I had set up DT Register on a website locally (using MAMP). In the listings of events, the blue "register now" button appeared at the bottom of each event listing.
Now, I've moved the site to the real server - everything is working great, except for the image path to the .png image that is the button. The link is still there, and the image is in the proper directory. I've quadruple checked the file path and it's fine. I've even set file permissions on the image to 777. Other images from that directory (the "blue" theme images directory) work fine.
The file should actually be 644 permission... and the directories 755. If the file is really there, no reason why it shouldn't load. Maybe try reloading the file.