Wireless going dead after perhaps half an hour

Hi all I've got a 1 week old XPS1330 with Vista Ultimate, and everything is pretty much as the factory configuration. I'm having a problem with wireless networking. There's no problem with my wireless network, I have confirmed this with a friends laptop and also my mobile phone. After I boot the XPS, it finds my local wireless network just fine, and I can use it perfectly well. However after about half an hour or an hour, it ceases to be able to find the connection. When I click on "Connect To" from the start menu, nothing happens on screen. When I click a second time, the Connections screen comes up on screen, but is is blank and is "busy" for about 30 seconds, then it will show the local wireless connection but says that I am "Connected with limited access". I've checked with the router firewall, and all permissions, conditions, settings etc are the same as for other laptops/desktops that work OK. Also when in this state, the "Find Wireless Networks" button on the right hand side of the laptop does not work - it does not bring up the wireless manager as it does do when the XPS is operating "Normally". Any attempts to do anything with the wireless/network screens also appear to hang for quite a time, and often end up not responding. A reboot sorts out everything, and then it is working again fine for half an hour to an hour, then the problems start again! Has anyone experienced this, or know what I'm (or the XPS is) doing wrong?