Export in FCP 7 taking far too long
 

Apologies if this topic has already been covered, but I am wondering why my 50 minute project could possibly take 11 hours to export to Quicktime. I am editing on my Macbook Pro (2.4 GHz Intel Core 2 Duo with 4GB RAM) and the project is a mixture of XDCAM50i 35mb/s and Apple Pro-res HQ, with one or two MP4 clips and nothing too complicated edit-wise on the timeline, and all footage is coming from an external USB drive. I understand that the drive will have something to do with the problem, but not to this extent. It never took this long when I was cutting with FCP 6. Any suggestions?