I didn't see if the problem was addressed in a later message, but it does appear that CMPro (even 3.10) seems to have a problem with some CD/DVD drives. I was getting the same error that OP was, so on a hunch, I copied the update files to the hard drive (and change the addpath to point to it) and sure enough, it works correctly. Almost seems like the program is trying to write to the CD/DVD and (obviously) can't.