Upgrade from 11.0 fails

I am trying to upgrade my 11.0 system which boots OK. The 11.1 DVD checksum is ok but after selecting Installation, a blue screen message “Make sure that CD No 1 is in your drive” appears. Selecting OK just repeats the process.

Run the media check from the dvd in addition to the checksum.

Thanks for the tip. It wasn’t the DVD but the drive. Put a new one in and upgrade is in progress.