Live CD severe problem in connecting to wired net.

Hi So I finally gave the Live CD, which is based Ubuntu 14.04. The wireless works fine now. But I have a sever problem with the wired network, which installed via the systemsettings. Every 1 min the net is gone, inspecting the error: the default gateway is deleted. So I have to reconfigure the net, but every minute makes it a PITA. The file in /etc/network/interfaces is fine though I never faced that problem before (Using trinity 3.5.13 on Lucid and even using R 14 on Kubuntu 14.04 (which gave me a problem with wireless, but not that sever problem)). I summarize: - Kubutu 10.04 + Trinity 3.5.13 everything is fine. - Kubuntu 14.04 + Trinity 14.04, wired more or less ok, wireless has a problem with tdenetworkmanager, wicd works fine though. - Live CD based on Ubuntu 14.04, wireless tdenetworkmanager is fine, wired net breaks down every minute when configured by systemsettings. My most pressing question, how can I get the wired net to work. Thanks Uwe Brauer