First of all, take a look at the logfile, dvdwizard creates. The file can be found in the directory, you called dvdwizard in and is named dvdwizard.log. You should get a hint on what is wrong there and maybe you are able to resolve the problem by yourself.
The next step: look into the mailing list on http://sourceforge.net/mailarchive/forum.php?forum_name=dvdwizard-users
If you're not that lucky, I suggest downloading the latest version of dvdwizard as a snapshot and retry.
Still not working? You should then search the FAQ and the mailing list archives. Maybe somebody had similar problems before and was able to resolve the situation.
If this doesn't help either, report your problem in the bug tracker on the Sourceforge pProject page. Please include a tarball with at least the log file and the command file (named dvdwizard.cmd in the working directory). Be sure to mention the Image Magick Version, you are using.