FreeBSD DVD, CD Installation problem

[Andrew M]

I was trying to install Freebsd from dvd, but after dvdrom starts to 
read the disc, comp reboots, at first I thought that it's dvdrom fault, 
but any other disc starts without problems. Then I tried cd, neither 
dvdrom nor cdrom reads it.
I found FreeBSD 7.2-RELEASE Errata which explaines cd1 bootable problem.
Cdrom does recognize the i386 bootonly or livefs as bootable, but right 
after disc starts it reboots machine, just like with dvd case.
I just tried 7.1 and it's the same problem, system reboots right after 
dvd starts.
Any Idea what is it, what might cause it ?, is there any workaround ?.