OK. I solved this. Due to problems with Linux USB 3.0 I deactivated the legacy USB support. After that the USB stick and the USB cdrom were no longer visible at boot time.
Activating this option solved my problem.
OK. I solved this. Due to problems with Linux USB 3.0 I deactivated the legacy USB support. After that the USB stick and the USB cdrom were no longer visible at boot time.
Activating this option solved my problem.