I seem to have no end of networking issues recently.
Last night, Andrea had to reboot an Acer 5003 laptop to do some online banking in Internet Explorer. The machine hibernated. When I rebooted in Linux this morning, the ethernet failed to work.
I rmmod'd the module (sis900) and modprobed it back but no go!
"dmesg" gave the following hint:
eth0: Media Link Off
That churns up lots of hits in Google, the few I read weren't useful, since these people couldn't get the port working at all, and I know that it was working yesterday.
So I rebooted into windows and ethernet was working fine there. I shut windows down completely, (no hibernating), and got the following:
eth0: Media Link On 100mbps full-duplex .
I'm not sure what was going on there, but I'm not going to to touch it...
Hope this helps someone...