Posting this because I've been practically pulling my hair out trying to fix various laptop issues that have been randomly disconnecting from Wifi. No matter what router/wifi connection you connect to the same intermittent problem happens. Turns out all these laptops have one thing in common and it's called the Intel Centrino 1020 wireless N card. Chances are if you have one of these model Dell laptop you have the 1030 chip (there are other brands that use it as well):
Inspiron 14R (N4110), N4120, 17R (N7110)
Vostro 3450 3750
XPS 15 (L502X)
XPS 13 (L321X) Ultrabook
XPS 15z (L511Z )
The offending Wifi card (hate you!):
Do yourself a favor and get that piece of crap wireless card replaced. I opted for the 6230 model. Luckily the card is under the bottom access panel on those Dell laptops so it was a quick fix to replace and update the drivers. Now all my clients are happy!