Not playing in preview or not playing after export, in a viewer? How long is the project and what is the resolution of the bulk of the files that it contains?
When you say "not playing" - what, specifically happens at the five minute mark? Share the project and someone will check it out and likely solve the problem.
http://nch.invisionzone.com/topic/23659-tips-for-getting-help-on-this-forum/
If it contains sensitive material link it in a personal message (PM). Click the envelope above. It won't be passed on or retained. Use FILE|SAVE PORTABLE PROJECT AS, not simply SAVE PROJECT, and don't forget to get a shareable, public link - not one that is restricted.