We found a solution to our problem, Update isolinux.

To accomplish this, download the latest syslinux package (http://freshmeat.net/projects/syslinux/) and copy the file isolinux.bin to
knx/master/boot/isolinux of remaster directory. See Knoppix Remaster HOWTO for instructions on remastering knoppix (http://www.knoppix.net/wiki/Knoppix_Remastering_Howto).