The phantom Network Shutdown, What the Heck?! Help!

Hey There, I have a simple enough network.. a netgear router and a standard PCI netgear wireless adapter on a secondary computer. When on the secondary computer, and I'm downloading files.. I've noticed that if it's a larger file and I leave it downloading for a prolonged period, as in hours, (but sometimes within minutes) the whole network will just lose its internet connection. This doesn't happen when doing other functions, browsing, mail, etc.. I then will proceed to unplug the router, plug it back in, and wa-la, its working again. Anyone know why my network stops like this? I forgot to mention that BOTH computers lose internet connectivity.