I had the same problem some months ago and I solved it installing a win 2003 compatible driver. I discovered a miss understanding with the name of the card and some drivers they call 8139 to the one that truly is 8L39 (8139-8l39)
The correct driver will search for "RTL8L39.SYS" and not "RTL8139.sys". Beyond this, 3 months later I have the same problem with a new machine installed with this SO. I'd try everything... and get nothing to work. One week later, after reading this forum, I sit on the machine again but this time with the mind in white, I changed the value of the variable, took the correct driver, plug the RJ45, and everything is working. I don't know what was, if one thing or the other... but... that is the solution, I think.
Using win 2003 enterprise
