Setting IP manually

[tudza]

I set my IP manually some time ago instead of using DHCP.  I need to 
change the IP addresses for DNS now, but the systemsettings tool simply 
does not work.  (There is no Administrator button as it claims.  I 
access it through kdesu systemsettings and it just sits at Reloading 
Network forever after I tell it to save settings.)

I do not remember how I managed to do this last time, I'm sure I hand 
edited some bit of XML file somewhere.

Is there an alternate tool or can someone tell me the correct settings 
file to edit?