installer does not find a network - but a live system does ... wtf?

[Andi Meier]

*Finding:* apparently I can *always* get the system to work. I only have to do this one time after boot:
  $ ifdown eth0 (output: "send_packet: Network is unreachable")
  $ ifup eth0
Then, network is there. Everythings ok. Just one time this ifdown/ifup combination.

Also, the output of "ethtool eth0" is different before this ifdown/ifup combination and after it - different in 1 line:
  before: Link detected: no
  after: Link detected: yes

Seems the problem is on physical/link layer. Why is eth0 always down initially after boot and why does the ifdown/ifup combination always
cure the problem?

Andi