I also had this problem with my Dell Studio 1557. The laptop was new to me, only had it for 2 days so was unfamiliar with it. I spent hours looking for a fix, to me there was no reason why the wireless would just stop working, at first I thought it maybe overheated and broken the card (The higher processers in the studio range tend to overheat). I had only put the laptop down for 10mins, came back to it and the wireless was not working at all. I finally found the problem after i'd given up, my kitten must have walked across my keyboard hitting the F2 key which is also the wireless key for turning it on and off.. I had not noticed this key before, I had only been looking for a wireless switch on the laptop elsewhere, how stupid I felt after all of the effort I went to trying to fix it :)