Comment 26 for bug 573259

For me shutting down the system, unplugging the power supply, waiting a minute and then restarting solved the issue, at least by now.

I have Lucid Lynx 32 bit, kernel 2.6.32-26-generic, and the network adapter stopped working with no apparent reason, after a month or so of normal use (well actually a couple of strange system freezing happened).
The motherboard is an asus p7p55 LX and the card is detected as "RTL8111/8168" controller. Driver was the default one, r8169.
It is now Realtek's one, r8168, but installing it didn't work by itself (but I hope it will at least prevent the freezing issue).

I got the problem fixed only with unplug. Simple reboot didn't work, leaving the pc shut down for a day (but with the power cable still plugged) didn't work, a lot of other stuff didn't work... only after restart *and* unplugging I got the network working.

So, unplugging is worth trying.... fast and harmless, and it could solve. At least for a while.