router quirks

i have a linksys BEFSR41 router installed—i am on a fixed wireless LAN–the router works fine,but i keep getting”local area connection–network cable unplugged” messages.i have checked all fittings on the cable and on my pc connection: there are no obvious loose connections–would appreciate it if anyones has any ideas as to what is going on.my system is an AMD XP 2000+ , with 512 MB memory and a 40GB HD.