Laptop loses internet connection?

I run Windows Vista on an Alienware laptop. I had to recently reformat my laptop and now the internet is flaky (before it worked perfectly.) It will consistently find the wifi signal when I first turn on the computer, it will stay connected for an indefinite amount of time and then lose the signal and "not detect any networks" (no matter how close the computer is to my router/modem.) Connected through an ethernet cable it works just fine. I am using a Cisco Linksys 1000 wireless router if that makes a difference. Any suggestions?