ifup Knetworkmanager problem

I’ve got problems installing OpenSuSE 11.2/64 on HP machines.
This particular machine is a HP DC7800 (C2D 8Gb VT-enabled, Integrated Intel 82566DM Gigabit Network Connection)

After installation the network connection (DHCP or static) works fine if KnetworkManager is selected. When selecting ifup communication stops (cant ping external IP, cant surf etc.), switching back to Knetw.Mgr enables ping etc. immediately.
(Doublechecked ip-address, g/w etc)
(I’m not new to Opensuse11.2 /Xen installations, (but I,ve never installed OpenSuSE11.2 on HP), so i dont know if this is hardware-related, network board-related etc.)

Trying to install dom(u):s in Xen Virtualization (in KNetwMgr mode) complains about VIF-bridge (the bridge is created by Hypervisor & Tools) but the dom(u) installations fails & complains about the vif-bridge, so i DO have a communicationproblem…
Any ideas how to troubleshoot ??