H, I have just read this thread with some interest, and as such i would just like to inform all you 1558 owners that you are not alone, 1557,and xps owners with the 15,16&17 models have all experienced the same problems. The fixes have been pretty much the same useless replies that you have been getting, dell technical support is worse than useless they make up fixes as they go along none of which have worked by the way. At the moment i am waiting on my 1557 being returned to me after it has been back to dell for another so called fix, i have had mother boards replaced ram ,heat sink and fan and tried different wifi modules all to no avail. The best i have had is a week without a problem, but now it seems my bluray drive is not working correctly so back it goes. Dell support is rubbish the so called tech guys that rarely turn up on the forums unless things are going well or they want to remove a reply that they don't like that is, have no answers the replies that i have seen here from them is laughable not heard or seen the problems have a look at the hundreds of posts on the XPS or 1557 threads. I know that this is not of much help but at least you know that you are not alone with your issues.
The best fix i have read anywhere is send it back and buy something else, A very disgruntled dell owner( i have owned, bought and recommended hundreds of dell PC's not any more not a chance)