I think I saw something in the docs that you can do a ctrl-alt-f2 to open a text console, type the command startx and that should bring up the ubuntu desktop. Once both are running, you should be able to switch between the Desktop (ctrl-alt-f7) and the LMCE desktop (ctrl-alt-f11).
I also have a dedicated core but would like to access the KDE-desktop. I tried ctrl-alt-f2, entered username and pw and tried the startx command. It sais it's allready running. Then I entered crl-alt f7 and all I get is a blinking cursor where I can't enter any commands. Does nobody at all uses the system this way? There are a few topics on the forum about this issue but nowhere there is a correct answer. If you know how pls let us know.