Wireless LAN

I have recently purchased an Actiontec ADSL Router/Modem and a Linksys USB Wireless NIC.

When I switch my XP machine on I can connect to the internet quite happily, however after a short period of time Internet explorer starts sayin page cant be found. When I investigate the wireless connection has failed. If I reboot the router and reconnect all is fine again for a short period of time and it happens again. Can anyone give me any pointers ? Thanks