I had the same issue and ultimately solved it with two changes to my network. I've sinced backed out the changes one at a time and confirmed that both changes were indeed necessary. I've been rock solid for a month now.
First, I am running AT&T's UVerse and am stuck using their 2-Wire 3800HGV B router as my DHCP server. I found that approximately once a week, DHCP would freak out, kicking my iPad off the network and not allowing it back on. Sometimes it would take a few reboots to get it to calm down. Since I need the 3800HGV to run my TV, I hung a NetGear wireless router off the 2-Wire router and created my home network on the NetGear. The 2-Wire router is now in its default configuration and provides signal only to the TV and the NetGear router.
Second, between using a consumer grade router and the challenges that iPad has with its antenna, the iPad would drop constantly. Initially, since I had a few wireless routers sitting around, I set them up as access points (turning off all of the router functionality) to cover the deadspots. Something about the multiple access points seemed to confuse the iPad making it drop off the network, so I added WiFi repeaters to cover the dead spots. Problem solved.
Sorry if this seems a bit complicated, but I hope it helps. Bottom line, if you're using UVerse, isolate their router outside your home network and don't over complicate your home network.