In previous opensuse versions, it has been posible to enable vnc administration easily by enabling the service in YAST.
In OpenSuSE 11.2, this option is still available, but does not work well by default.

The issue, I believe is that the default window manager has changed to KDE4. Although KDE4 is the default window manager in 11.2, I still use GNOME.

When connecting to the vnc server on display :0, all that's drawn is a black screen with a gray X. To fix this, I changed the default window manager to gnome, and the default display manager to GDM.

These settings can be changed by editing the files in /etc/sysconfig, or using the /etc/sysconfig editor in yast.

Set DISPLAYMANAGER to 'gdm' and DEFAULT_WM to 'gnome'

You'll have to restart the X server, and after that, remote connections via VNC will open up gdm and allow you to log in.