network interfaces not coming up

[fuzzy_4711 gmx de]

Hi list.

I am using xubuntu 12.04 32bit on a dell vostro 1720 laptop. I would like to use network-manager but it is not bringing up my interfaces (eth0 and wlan0).

/var/log/syslog says, when enabling networking:
eth0 now managed
eth0 device state change: unmanaged -> unavailable (reason 'managed') [ 10 20 2 ]
eth0 bringing up device
eth0 preparing device
eth0 deactivating device (reason managed)

ip li sh shows both links, udev-rule is loading them with correct mac addresses, but state is down.

Drivers are loaded, at least I would expect running eth0...

Could you please advice?

Thanks
fuz