I think it has to do with WEP as you say. Apple has issued a warning about it. But I can't replace my router because my provider issued a warning that I don't.I've also had mixed results in different areas. Personally I am certain its more of a router issue or at least certain routers/security type (WEP,WPA,WPA2) not preferred by the iPad. In my apartment I have a Linksys and never had issues, at work we also use Cisco and in my various cafes they are an assortment of brands and I have never had connection problems...however, my in laws have a d-link router and my iPad consistently loses its network key every 15 minutes or so if constantly online.
Apple said that there would be a software fix. Where is it?
Why not try changing the security to WPA/WPA2?
I am running WPA2 on my Airport Extreme and have no issues at all with multiple iMacs, multiple iPads as well as laptops and multiple iPod touch devices and iPhones.
Just a thought.