Try restarting the program and then register again. If the registration keeps failing, please contact us at email@example.com and let us know the exact error message you're getting. If there is no error message but pressing the 'OK' button simply doesn't do anything, have a look at your console log, see if there are any messages from DVDpedia. You can access the console log via the application 'Console', located inside your Applications/Utilities. The newer messages are towards the end of the log. If the error is a difference in architecture:
/usr/lib/libcrypto.0.9.dylib: mach-o, but wrong architecture
This means there is an error in the eSellerate engine. Try this:
To force DVDpedia to install a fresh copy, go to /Library/Frameworks folder on your hard drive and remove any folder that starts with "EWSMac" (when removing this folder it will ask for your password as it's on the root Library folder). Also check ~/Library/Frameworks in your home folder and not the root library. Do this with DVDpedia not running, then launch DVDpedia and try to register again.