Apparent intermittent NIC failure - connection drops randomly

Looking for advice before I go to Dell Support. I have a 7-month old Dimension E310, with an Intel Pro/100 VE NIC, running XP Home SP 2. I have a 2Wire DSL modem connected via Ethernet cable to the NIC. Approximately 80% of the time now, everything works fine. (And months ago, it was 100%, but the percentage is decreasing.) But 20% of the time, the NIC lights (orange and yellow) both go off at a random point (whether I'm working on the computer or not) and "a network cable is unplugged" is reported. Reseating the cable in the computer or the modem does not help. Switching out a different cable does not help. But when I plug that end of the cable into my other computer (a Latitude D610), it reports a connection right away. If I plug the cable back into my Dimension, it's still "dead." However, if I leave it there, a few minutes later, without touching anything, the network connection will usually come alive again and I'm online.

 

So I suspect the NIC on the Dimension itself. I have run every troubleshooter and diagnostic I can find, and nothing reports a problem with the NIC, even if the lights are off. I only have one driver profile for the NIC, not multiple ones. I have run the loopback test that I have run by booting to the diagnostic partition (F12 on boot) - the yellow light on the NIC is hammered, working fine, reporting no problems, but the orange light remains off. Upon rebooting, orange light may or may not be back on, showing the connection. I ran the other NIC test in that diagnostic as well - also no failure found. I have run both tests many times, with no failures.

 

Luckily, however, I have a USB network connection into that same DSL modem so I am online whether or not my NIC is working (for now).

 

Is this a simple case of a faulty NIC that doesn't think it's faulty? Anyone have ideas before I beg for a new motherboard from Dell?

 

Thanks in advance,

Dr TKT