There are to ways to do this:
1: If you have your system up and running (and up to date) you edit your /etc/pluto.conf file and set autostartmedia = 0
2: If you are going to install a new system edit mce_wizard_data-(single/double)_nic.sh and set c_deviceType=1 (1=Core, 2=Hybrid, 3=DiskedMD)
Also if you read the release notes from 2.36 under pluto-boot-scripts (234) it states:
- Do not start X, if AutostartMedia in pluto.conf is not 1
I would go for the first solution it seems that if you are running mythtv the backend does not get installed plus you might want to run mythsetup.
I had similar issues with VDR.