Compositing unknown error

Day before deadline, and technology is not my friend today. I have composited all the individual shots of my film have been exported at ha very high aspect. It toke almost three days and when I put together all the scenes and music the current computer I was on did not have a present setting for quicktime. So I exported it of a preset of H264 and made sure it was 25 fps, 1920x1080 and was square pixels. However when it exported it did play very nicely on a Windows player but on quicktime it was jumpy even though the frame rate was right. So as soon as I saw that the video was jumpy I went straight to another computer, linked up all the files again and tried to export but it just said unknown error. I tried to put the output in numerous locations but it made no difference. Then the uni closed, to I toke my wrong codec export file home and hopefully will get up very early and try again tomorrow morning.