I recently shot a wedding and was able to export pretty much all the files except the ceremony. When i try to export the file it will say general error illegal file name or something to that effect I have also tried transfering this footage to another drive and it wouldn't transfer because it said the file couldn't be read or written.
With the limited information provided in your post, the only thing that comes to mind is that the HD you are saving to is not formatted for Mac (OS journaled). If the HD is set to FAT 32, your file size limit is 4GB. Assuming that the video format of your project is PAL/NTSC or HDV, if your video duration is longer than about 20 mins, you will get an error when saving your file as anything longer than 20 mins will be more than 4GB.
All the best,
"Is it me or do I spend half my life watching little grey bars turn into little blue bars??"