The playback rate control affects only playback and not renders. You will have to speed up your video either by stretching the Events (Ctrl+Drag the edge of event) or using Velocity Envelopes (search in Help).

If you have lots of events, it may be easier to render the project to a DV avi file, then load up this avi and change it's speed** with the methods mentioned above and re-render a new clip.

**You can right click on an event, choose properties and type in a new playback rate. Then drag the end of the event to resize it to the new length required (by default increased rate will produce a 'loop point' in the event; decreased rate will chop of the end of the event. Easier to understand when you do it).