Membership contribution page leads to "Not found" error
Most likely, if the test drive page is working and the live page is failing, your CiviCRM base page isn't set up yet.  On Civi 4.6, this is supposed to happen automatically, but either a) you upgraded, or b) I've seen plugins that interfere with the alias naming process.

In CiviCRM, go to Administer menu > System Settings > CMS Database Integration.  Note the "Wordpress Base Page" setting.  Next, in Wordpress, go to Pages > All Pages.  Make sure that page exists.

Last time I had a plugin interfere with the naming process, Civi had created a base page called "CiviCRM", but I had to go in and manually edit the permalink to match the base page setting.

Hopefully this clears up your issue!