Codec not found

I recently switched over from a G5 to a MacPro Intel. FCP works fine except that when I now try to create a QT movie from a project (File, Export), the conversion starts and the progress box gets about halfway, then stops and I get the following error box:

"Codec not found. You may be using a compression type without corresponding hardware card"

This occurs no matter which codec I use. Any ideas what might be happening?

Thanks,
Stan