Usually that indicates a corrupt clip. Try Duplicating the Project and then cut it in half. If one half causes the crash.Export the other half as a separate file.
Then you can bisect the "bad" half and further isolate the problem.
Sooner or later, you'll figure out where the problem is.
See if you can simplify or export just the problem area as a separate clip
Once you identify the rogue area, you have options.
If you're in a hurry, you can then re-assemble the project on a new timeline using the exports.
Or work on solving the problem area - as you choose.
Know someone who teaches video editing in elementary school, high school or college? Tell them to check out http://www.StartEditingNow.com - video editing curriculum complete with licensed practice content.
If I had purchased Digital Rebellions Pro Maintenance Tools, used Corrupt Clip Finder/Crash Analyzer/Media Salvage and had good results, I would recommend it. But I haven't, so I can't.
Bet it's a good buy though.
Is there anything that might be suspect around the halfway point (or right at the end, I notice most of my exports actually finish at 50%). If so, turn off or disable that effect/clip/image and try to export again. If there isn't any specific plugin or effect etc. you think could be a potential problem, Bill's process of elimination is a good method. I'd probably start with a test export of about 1/3 of the timeline, centered on where you think the problem might be and repeat. Trading likelihood of correctly guessing the problem portion, for faster test exports and more accuracy when found.
You could also try logging in as a new user and try to export, or deleting all render files, trash prefs and repair permissions.
Don't forget to report back here with the cause, once you find it.