You can configure your IP address with YaST, but in this case you need to switch from KNetworkManager to ifup contorolled method in Network Devices > Network Settings. To modify the IP address select your card and hit edit.
same here using KDE 4.2 from factory and knetworkmanager (KDE3). I use knetworkmanager for sync with AP (and WEP/WPA configuration) and then “dhcpcd wlan0” from console. With wired networks no problem.