MacBook Pro wireless problem!

My mum got a MB Pro a few days ago it connects to my O2 router fine but accessional it disconnect for parent reason you have to got up to the menu bar ad select the access point manually to join again. I have a late 2006 iMac 17" intel that connects fine to the the access point no problem we have had the o2 wireless router for about 12 months now and i've never had problems before apart from i have to reset the box very rarely for the net to work again. so any help please.
cheers all.

That sounds like a defective Airport card in the MBP. I'd take it back to Apple on a warranty claim.

Does it happen with other wireless networks?

It only happens on the O2 wireless router at my dads house he has a sweex wireless router and it never disconnects from that, I don't think its anything todo with mb pro think it might have something to do with the router. May be the airport card in the mb is not 100% compatible with tis router.