Nate you pointed me in the right direction in solving my “General Error” problem. So I rendered segments and isolated the problematic clip.
It was on a clip that had speed ramp to 13000+%. The huge number didn’t seem to cause the problem (FCP6) it was the clip’s audio track which was also affected by the speed ramp.
When I deleted the audio track the clip played back fine and rendering/export was successful. I didn’t mind losing the audio because it wasn’t needed (at 13000 people sound like cheering mice)
General Error is so general, but hopes this helps someone else.