[Ken Dinsdale] "I get approx 3 minutes in and it crashes."
What do you have on the timeline at the about the 3 minute mark? Perhaps a large image? Maybe a VideoFX that is sensitive to the project size (which you changed)? Can you start after 3 minutes and get it to render? You need to determine what about the timeline is causing it to crash at that point.
~jr
http://www.johnrofrano.com
http://www.vasst.com