To troubleshoot these types of errors you have to follow the steps below in order until you contest displays correctly:
a) Make sure you go to Settings -> Permalinks on your Wordpress admin
b) Ensure you have the permalinks set to something other than the "Default" setting.
c) If you had permalinks set to "Default" make sure you change it to a different setting like "Post name" then save.
d) Go to your contest page and see if it displays correctly. If you can view you contest you can stop here, otherwise continue with step 2.
a) Go to your Plugins -> Installed plugins on your Wordpress admin.
b) Start de-activating plugins one at a time. After de-activating each plugin, go back to your contest page and try to re-load the contest page. If you got your contest page displaying correctly then you have found the conflicting plugin.
c) If you contest is still not displaying correctly, continue de-activating plugins one at a time and repeat b) again until you find the conflicting plugin.
Note: please share with us any conflicting plugin you find, so our development team can check if there is anything we can do to avoid conflicting with any particular plugin (for future updates of WP Contest Creator)