Wifi rage issues

Hello all,
I have a a Macbook that is running on 10.6.4.
I have been having issues with the wifi for about a month now.

The issues are: My range is basically zero, I have to be in the same room as the router to get wireless connection. I will walk in another room and I lose all connection at once.
I've brought it to the apple store and as usually they were no help.
So I am turning to you all for help.

Please HELP!

-Tom

What is your router?
What frequency are you running?
What happened during this month that changed?
What does iStumbler say about signal strength and interference?

It could be a myriad of things - the more info you can provide the better chance you have of getting a meaningful answer.