If you can identify the exact frame in the timeline sequence the render is failing at (or general area at least), look for a 1-frame gap between clips, or a glitch in the video or something that might be causing this failure.
Also note that when getting ready to Export a video, there is no need (or good reason) to first Render the timeline, simply Export and video gets rendered direct to final output format at that time. The "Preview" files that get created with a pre-render are not even used for the final export anyway - unless you specifically select "Use Previews" for Export, but even then those previews typically have to be re-rendered to whatever the output format is. Now you've added time to the process (rendering twice) and probably decreased the quality (by rendering twice) as well.
Thanks
Jeff Pulera
Safe Harbor Computers