isolinux: Extremely broken BIOS detected

I'm booting the Slackware 15.0 DVD using a ASUSTeK P8Z68-V motherboard. When the DVD starts booting I get the message, "isolinux: Extremely broken BIOS detected, last attempt with drive = 9F". Despite that message, it goes ahead and continues booting. However, if no hard-drives are installed, after it get to the line: "Triggering udev events: /sbin/udevadm trigger --action=add", it stops for a minute or so and I can hear the DVD "seeking" a lot during that time. Finally, something times-out and it continues booting.

Any idea what is causing these oddities? I've been using Slackware for over 20 year and have never seen this behavior before. If this is something to do with this particular motherboard I can use a different one.