Running yast2 from the command line should open up the graphical version of yast, rather than the command line version. Running yast from the command line is what’s supposed to open the command line version. Sounds like something went screwy and names got messed up. Try running yast from the command line, see if it gives you the graphical version. If so, then just switch the names for /usr/sbin/yast and /usr/sbin/yast2.
yast2 falls back to the text version when it cannot open a connection to the X server… The root session in the terminal has no cookie to connect to the X server with. So that explains the second observation. yast would have given you the same result.
Who are you logged in as when you click on the YaST icon, yourself or root? I would guess yourself, as it looks like it has finished asking you for root’s password and is trying to run yast2. But it seems to have encountered a problem opening up a window (surprise, surprise). Are you logged in at the console?
Have a look in /var/log/YaST2/y2start.log to see if there are any distress messages there.