My head is exploding

Hi all.
I am having much grief here.
I have a linksys BEFW11S4 in the loft.
One computer hard wired through it and one computer and a laptop wireless.
The connection kept dropping so tried another router, not new but newer.
This one also keeps dropping connection and also I now have a problem with the laptop not being able to browse the internet using IE, or able to get updates yet it gets connection to p2p networks so is having no problems connecting to the network.
The hadwired comp and the other wireless comp hve no probs except whenit drops. Only the laptop is havong grief.
Am i missing a setting on the laptop?
Cheers.

 

Cheers Tim.
I haven't had to go down that route yet, (goes on a bit dont it!!), I reset the router to factory defaults and started again. All comps working at the mo.
There were some conflicts, the router had assigned the same ip to two computers, also, according to a site survey, there are about four other wireless setups within range so we may have been clashing channels.
I have also disabled the WEP and gone down the mac address route instead.
Have to see how it goes.