On further investigation, the Ubuntu-Feisty version of genisoimage (9:1.1.0-1) running on edgy also does not have this problem! I understand genisoimage is a fork of mkisofs now used in preference to mkisofs in etch and edgy.
I.e. This problem is edgy specific as far as I can tell! -- mkisofs doesn't properly convert lower case filenames to upper case https://launchpad.net/bugs/70098 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs