3com 10/100 Mini PCI Ehternet Adapter - unplugged message

hi,

I have two dell laptops

1. Latitude D630

2. Latitude C810.

The D630 works fine plugged into my network router via a network cable but the C810 using the same connection does not have a light on the network socket and says Network Cable Unplugged.

The C810 has a new XP build SP4 and when I look in the Device Manager it does not report any network adapter issues.

Do you have any advice please.

Thanks

Lee