I've had the problem. Just a few hours ago, I reset my wireless router from "b and g" to "g only" (based on the advice of others, not some brilliant insight on my part) and it appears at first blush to have solved the problem.
This (apparently!) works at home, but I'm not sure it will work so well when I take the iPad on a trip and ask the Hilton hotel to please change the settings on their wifi!