I see that the "network cable unplugged" message is a common issue.  Well, I started getting it too, and I've replaced a lot of hardware and can't seem to find a pattern.

Inspiron 4000 w/ Advanced docking port.  The PC is on 10-12 hours a day during the week, and often over the weekend.

Inspiron built in NIC port works fine both at work and in the office.  I've been using them for 3 years

About a year and a half ago, I got the docking port for my office.  I've been using it with no problem for a year and a half.

A month ago, I started getting a "network cable unplugged" error message.  It would pop up after the computer was on-line for an hour or most of the day.  There was no rhyme or reason as to how long I could stay on-line before the problem occured.  Sometimes it would lock up the computer completely requiring a hard reboot.  Sometimes, I'd just been unable to browse web pages or get my email. 

If I disconnected the Ethernet cable from the docking station and attached it directly to the laptop, I would have a good connection and no problem.  As i said earler, If I bring the laptop home and direct connect, or wireless connect to the internet using our cable modem and D-Link wireless router, it works with no problem.

So - I figure the problems the docking station.  Since it's a year and a half old, I can't see spending $100 to getting it repaired so I buy a new one.  It works perfectly for two days.  Then I start getting the "network cable unplugged" message again.

Is it possible there's a failure in the interface between the laptop and the docking station?  I can't think of any other possibility, as i have swapped out every other component I can think of.

I installed a new hard drive in the Inspiron last January and bought a new copy of Windows XP home which I installed, so some of the drivers were from the WinXP installation instead of what Dell might give you.  But, then again, the PC worked without a hitch from January to September, so the idea of having the wrong drivers seems kind of moot.

Thanks in advance for your suggestions and knowledge . . . .