RHEL6u6 workstation (64 bits) can't make bootable DVD

Downloaded the recently released rhel-workstation-6.6-x86_64-dvd.iso file, made a DVD as ususal for a new install.

My system just won't begin to boot from it, no error messages seen, just goes to another boot device. Checked the sha256 sums on both the downloaded file and DVD, they're right. Made a second DVD, same result. However, the 32 bit workstation iso is bootable, no problem. Other install disks work also.

Anyone else seen this?