I have the same problem with my Acer Iconia w700.
I have a D-link 655 router.
I have a win xp laptop, a HP stationeary with Win 7, a HTC with android and all of them work fine on my wifi. But the Iconia gets limited connectivity all the time, and some time it does not find any wifi at all.
Ive alos updated the router sw.
Any tips?