iPad won't accept WiFi captive portal logon
alright I may have some light to shed on this:

I just got off the phone with an Apple Engineer and he said a few things to me that make sense.
He has stated that the "crippled browser" should never be displaying any other page than
our captive portal page. He stated that if after logging into captive portal I am redirected
to www.apple.com/library/test/success.html the iPad's "crippled browser" will close.
If I see another page (like I saw apple.com and not http://www.apple.com/library/test/success.html which would have closed the browser.) it is likely that the system hosting captive portal is not directing me to the exact original page requested. Which was http://www.apple.com/library/test/success.html 
It could in fact be truncating or altering the original URL, which is possibly why I see apple.com's main page in the "crippled browser"

No resolution yet, as I still need to confrim that the wireless controller is indeed doing this, but it makes sense, and might help.