Windows 7: Can't connect windows 7 wireless with lenovo laptop

Hi, first time user here and normally i'm pretty good with this networking stuff but something has come up that's baffled me..

So i'm trying to connect this lenovo laptop running windows 7 to my home network, (I have a 2 wire wireless router provided by my adsl company) the laptop can see the SSID and connect to it but the thing is when the computer is sitting right beside the wireless router on the table, the wireless seems to work just flawlessly. The moment i take the computer away (out of the room) I lose the wireless connection and nothing works.

my router is downstair and upstairs I have a macbook, wii, and ps3 all running wirelessly (and flawlessly) from this router but this laptop with windows 7 doesn't seem to want to work unless its right in front of the router.

I've dealt with my ISP on the phone as well as Lenovo tech support (ran all the driver updates and cpu updates) and now they're all throwing their hands up and the last thing lenovo says to do is a system restore...

anyone have any ideas or seen this before? If i plug the computer in with a cable it all runs fine. could a windows 7 update be an issue.. not sure its been updated in quite sometime...

any help would be greatly appreciated.

Cheers.