cdrecord/mkisofs ?

If I take a CD, such as one of the SuSE CD's, and do to following: dd if=/dev/cdrom of=isofile Every thing completes with no errors. Howver if I create my own cd using the following: mkisofs -V "MYLABEL" -R -o ./cdimage.raw ./directory cdrecord -v speed=8 dev=0,2,0 ./cdimage.raw and then try the same dd command above using the cdrom as the reader I get dd if=/dev/cdrom of=isofile dd: reading `/dev/cdrom': Input/output error 5183+16 records in 5183+16 records out I can mount the iso file and see that everything is in fact in the file that was on the cd but but why the error when I make my cd and not one from a "valid" source?? Any clues???? Regards Mark