Hi,
I am having the same wifi internet connectivity issue with my Toshiba Sattelite laptop which has Windows 7 Home Premium even though other devices like my windows phone mobile, Android tablet are having no issues with INTERNET connectivity. Another interesting thing is that I have used an external Dlink wifi usb adapter with the same laptop, I am having the same internet connectivity issue with this adapter too. Besides that, I have also used a 3G USB dongle for internet connection in the laptop. It also suffered the limited internet connectivity issue after sometime. So it clearly suggests that neither it is network card's issue nor its driver's but it is something that has a lot to do with Windows 7 itself.
Please note that in all cases, this internet connectivity issue is random. Everything is going fine, suddenly a yellow mark appears on network icon in the taskbar & internet connectivity becomes Limited.
I am sure this is Windows 7/8 issue.
Thanks
Shezzy