It looks like this is a long-standing problem with the Intel drivers. Check out the penultimate post at the end of this thread
. However, since the date of posting is Feb 17, the issue may still not be resolved.
Reading through the thread, other suggestions are to turn off Bluetooth (if you're not using it), turn off HT (greenfield) mode, or restrict channel bandwidth to 20MHz. Unless you live in the middle of a field, running dual-band at 40MHz is a bad idea and pretty anti-social. Using a wi-fi scanning utility will show you if you have any channel clashes.
If you still get no joy, try plugging in a wireless dongle. Of course, if the lappy is still in warranty, you could chuck it back at the shop.
Oops! Just noticed a typo. I did have "Unless you love in the middle of a field..."
Sweet Thames, run softly till I end my song,
Sweet Thames, run softly, for I speak not loud or long.