[eluser]Tim Brownlaw[/eluser]
Nah it'll be simple! The trick is knowing how to dig in and work your way back out!
That's the really fun part!
Although with your issue it's being a little difficult to see what's actually going on!
From looking at the jquery ( not how I would have done it... but that's just me ) it looks "ok".
CroNiX should be able to shine some more light on that!
What we need to do is make 100% sure that what you are sending is being understood ( which you say it is... ) and that the response is being correctly generated ( which sounds like it isn't ).
This is where you'd be testing on the server itself, and pretending to be the client.. so you should be able to create a dummy requester ie a new method or even controller/method that mimics your Form Data you are sending... and seeing that you get the expected result.
Are you on skype or anything we can screen share?