Netzwork does only work in recovery mode

[Andy]

Hay volks,

i installed the 7.10 desktop image.

i have got the problem that the network connection only work  when 
booting in recovery mode.

When i go to user mode (normal booting) i dont get information from my 
dhcp server and if i configure the eth0 manually by hand the values are 
accept by ifconfig and shown with ifconfig but i cant ping my router or 
some other hostnames/ipadresses. I dont come out from this Ubuntu pc.

The other pcs in the network are working without any problem.

Andy ideas ?

Andy