Best to start a new descriptive thread.
How long is the project and how many tracks?
What is the resolution of the bulk of the source files?
What is the export resolution setting and does it succeed at a lower resolution?
Upload and share the PORTABLE project (not the export) and someone will be glad to check it out. Issues can usually be solved or explained quickly.
The process is easy, takes little time and can be private...
Here's how... 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 link to post.