I was playing around with plasmas etc.. and messed up mine. This is how u fix it. If your still logged in. open a root xterm and issue "mv .kde/ ..kdebkup/ .
logout then startx.
As a last resort which happened to me. grab that live cd or usb you installed from load it up and mount your partition to see your linux drive then copy .kde over to .kde/ on your linux partition reboot and your done.Q anyquestions pm me