Somehow, I do believe this is after upgrading to kernel-3.1.0-46, my NIC has defaulted to 10 Mb/s full duplex, and the connection is very unstable - disappearing for an odd minute now and again. I tried setting it manually through the ethtool-command, turning off auto-negotiation and setting the speed without success.
This does the job though:
ethtool -s eth0 advertise 0x008
But how do I add it at boot? Kind of annoying to su and typing that in every time I start up the computer. Help would be very much appreciated