ok lets start,
q1, what type of connection are u using-ie what shares the network, is it 3rd party, auto or set ip's?
q2, have you watched the network connection- ie watch the TX/RX to see if stable or resetting to zeros?
q3, the most low cost fix maybe to put in a NIC card in the laptop, that will fix problem,do you have free service to return to place of purchase?
try
plugging into another machine
download nic driver reinstall 4 laptop.
ask your local IT shop to metre the lan for you, one will have the equipment.
fixes, pcmcia card,reload op, maintan machine,
i hope something helps here.