Wireless switch on but internet not working

Hello,
It mostly happens when I am downloading files for some hours.

While downloading for about 2 or 3 hours, my internet connection goes off though the wireless switch is on, the wireless light near the wireless switch goes off too. So, to connect to the internet I need to restart the computer. And again, same happens while in the process of downloading.

It usually happens while i am downloading. It rarely happens while I am not downloading anything or just net surfing.

I tried to solve this by reinstalling the LAN driver. But still this problem is there.

Does anybody know the problem with my computer?

I'd appreciate the help