This is probably a superuser.com question, but it isn't online yet.
The PHY on my NIC is blinking on and off ridiculously, and it should always be on. I googled it and found no answers, just questions.
http://www.google.ca/search?hl=en&q=eth0+keeps+restarting&btnG=Google+Search&meta=&aq=f&oq=
This is on Linux (Ubuntu 8.10) with a Broadcom 100Base-T NIC:
lspci output: 01:09.0 Ethernet controller: Broadcom Corporation BCM4401 100Base-T (rev 01)