It's your cable box, the thing that filters the internet out of the cable. You've got a cheap one and it can't do network recovery if there is a stack problem. Rebooting the box every couple of hours is the only way to fix it.

If you plug your computer directly into the box via ethernet and you don't have this problem, it means it's your wireless router. Cheap routers are a joke and they don't work for shit. A real wireless router runs about $200, I recommend getting one. My landlord had a cheap wireless router and I had the same problem, so I loaned her my Airport Extreme and it hasn't gone down once.