Network Error Message in XP

Hello,

One of my clients has a Windows XP workstation that is grabbing it’s internet connection through a Linksys router. Everything seems to be working good with the workstation, except there always seems to be an error message that says, Network Cable Unplugged, and then right after that message is displayed, it shows that the network connection comes right back up by displaying Local Area Connection, 10MB. He doesn’t seem to lose his internet connection when this happens, but it is mind-boggling as to why this message continues to pop up and go away on a regular basis. You see it once every five-ten minutes it seems. Any ideas on what causes this or what can fix this?