unable to run graphical(?) apps launched from console

Hi - I am not only a Linux but a Suse newbie, having tentatively made the switch from Redmond. Just got a 7.3 box up and running. I have run into a small issue where I am unable to launch any kind of a graphical app from a shell, most recently a Mozilla installer. Scenario: I became su, and launched Mozilla's installer via the command ./Mozilla-installer. I get the following errors: Xlib: connection to ":0.0" refused by server Xlib: Client is not authorized to connect to Server I also got this error when I tried to build and launch the graphical kernel config tool via the command "make xconfig" when I was rebuilding a new kernel. Can someone shed a little light on this? Thanks in advance - Matt