That can be cause by a corrupted render. Mark and in and out splitting the sequence in half. Try to export. See if it crashes. If not, move to the second half. Continue this process to zero in on the offending section. Once you find the bad render, mark an in and out point around it and go to Clip (I think) and select "Clear Render Effects In to Out".
However, since you didn't list your spec, just for good measure, are you using DNxHD media? Or is there a ton of AMA footage? Also, you could try exporting a "Same as Source" quicktime and compressing it using Sorenson Squeeze or Compressor.
Los Angeles, CA
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