I had troubles with the Ubuntu r8169 driver and my Realtek RTL8111/8168B PCI Express Gigabit Ethernet controller for a long time.

Finally it semms that I found a solution for a stable ethernet connections: The new r8168 driver (Version 8.031.00 - found here) seems to work quite good out of the box.

Just extract it, and run autorun.sh (as root)

# sh autorun.sh

Of course, you have to do this after a kernel update once again. Don’t forget this - It frakked me one time!

That’s all :-)