your wireless might be messing with your lan connection ...switch off the wireless for a few hours and test ....otherwise check if there are any new bios updates available

Try going to Control Panel/Classic View/Device Manager.  Click on the plus sign next to network adapter.  Double Click on the your wireless adapter and then click on the Power tab. Uncheck allow this computer to turn off this device to save power.

I do not have a wireless card however I did check just to make sure under connections and it only shows one connections.  Anything else I contacted Dell they want me to pay them.   Might get HP next time.

Thanks I had tried that it seemed to last longer.   But still an issue anything else and thanks.

Try this to fix your problem: http://support.microsoft.com/kb/928233/en-us