I have no idea where to start with this problem. I dual booted my mac mini with Ubuntu 13.10 by installing rEFIt. It worked awesome. My only problem was not being able to reboot but it didn't bother me. I only say this because I'm wondering if that had part of a role in this problem. I updated Ubuntu to 14.14 a couple weeks ago and I shut it down when I booted up I got the mac "bootup song" and blank white screen where rEFIt menu was suppose to start. Then it just sits there frozen. I tried manually shutting down and booting up again but same thing. I think something about the update on Ubuntu deleted rEFIt. Is there a way I can wipe the mac myself and possibly? I have everything backed up so I'm not really worried about the information. Is there a way to reinstall rEFIt when I can't get into any OS?
Boot from an Ubuntu livecd and then download and install refind, for that see How do I permanently install rEFInd onto my mac from Ubuntu (without using mac os) and Installing rEFInd Using install.sh under Linux.