I have a Blelkin N+ Router and I am having the exact same issue. The router works great for all my wireless devices (which are alot) except for my iPad, iPod Touch, and Apple TV. The Apple devices work for a while and then disconnect. I have to turn off and then turn on networking to get them back.
I set up a Linksys router hanging off of the Belkin, and it works great for the Apple devices, except then my Apple TV cannot see my iTunes library because they are on different subnets. Sheesh!
Anyway, I just updated the firmware on my Belkin router as a new version came out a short time ago. I will try my iPad on the Belkin again to see if it stays connected more consistently.
How do we tell the folks at Apple and/or Belkin that there is a problem here?!