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

[Andi Meier]

I have some news: I observed strange phenomena:

directly after boot: no network.

Then, I tried the following sequence of commands (in chronological order):

ifdown eth0 => send_packet: Network is unreachable
ifup eth0 => No DHCPOFFERS received [=> Network is unreachable]
ifup eth0 => ifup: interface eth0 already configured
ifdown eth0 => send_packet: Network is unreachable
ifdown eth0 => ifdown: interface eth0 not configured
ifup eth0 => bound to 192.168.178.35 -- renewal in 364413 seconds (!!! SUCCESS !!!)

I don't know if the network is stable now, I just saw that it works. I was also able to do a "apt-get dist-upgrade" without problems (took
approx. 20 minutes, downloaded some 300 MB).

Is there any sensible and rational explanation for this? Or does this indicate I have a hardware issue? What a coincidence this would be:
exactly when upgrading to 10.10 and going back, the on-board network controller goes nuts???

Andi