ok if I am understanding you correctly you are checking the md5sum after you burned the DVD... this is not correct.
You must check your md5sum BEFORE you burn your DVD.
I use k3b for my burning needs. when I chose the iso I want to burn it runs a md5sum check before it allows you to burn.
I am pretty sure all burning software does this for you. you should verify this number with the md5sum of where you got the Iso. there is always a link that says something about md5sum. if it doesn't match then DO NOT go through with the burn, find another sabayon iso, check out linux tracker, it's where I usually download my Sabayon iso'shttp://linuxtracker.org/
. If it does match then chances are you are good. unless if stated here and in other threads there truly is a problem with some of the iso's.
And the core cd is for advanced users it is pretty close to doing a gentoo install so using it is not recommended if you have no clue on how sabayon/gentoo work. I suggest you steer clear of core until you learn the ways Sabayon works and in extension learn about building gentoo. So stick with the Gnome or KDE versions of Sabayon, until you are comfortable with the command line
if you are new read the Sabayon wikihttp://wiki.sabayon.org/index.php?title=Main_Page
and the new users resources.http://forum.sabayon.org/viewtopic.php?f=86&t=16505
this page is extremely important. I have used it extensively, and it is a great help, I even used it when I installed gentoo because i was more comfortable with how some of the topix were explained.
Well good luck, I hope this fixes or you fix it some other way. Sabayon is a piece of art that is hidden in a distro. and for me it really is a great distro, it can do anything you want to do in linux, but it is not easy. Read EVERYTHING. this is important. READ READ READ.That is a must if you are going to understand Sabayon. the resources are there. but no one can make you understand them. you must understand them by reading and asking questions.