I'm dealing with the same issue. Had you made any progress on this issue? Seems to only be occuring on IOS.
what happens when you point your browser at the gateway?
ie, if you put http://(my domain + file structure to..)gateway.php into the browser
you should get "Zend Amf Endpoint"
if not then the path to your Zend Framework isnt set properly
I do get "Zend Amf Endpoint" - as well - the app works perfectly when testing on my desktop as iphone4 simulation and on android, just not on my 4s device.
as a side note, i can even browse to the gateway.php that I have set up via safari on the device. That makes me think that theres just some dumb http entitlement or "allow" setting for ios that I'm not finding.