Hi
Whilst Shane has a myriad of stock answers I only have one or two 😉
In my experience a General Error whilst rendering is most often caused by a clip on the timeline that has an inconsistent frame rate.
QuickTime doesn’t care if a clip’s frame rate is variable (as in a slideshow of differing length stills) but FCP can’t handle even the slightest deviation from the project’s timebase. And because the timebase is so fundamental to the essence of an FCP project, the error that it throws up is as general as it gets… 😉
My solution has turned out to rebuild the suspect clips – either by Exporting from QT Pro with recompression, or Conforming the clip to the project’s frame rate using Cinema Tools.
Of course you have the problem of identifying the culprit clip(s), but usually they are the result of a different workflow – composited or transcoded clips, and easy to spot.