It's a good idea to submit through AJAX. If they had a very well defined API, we could code for that on the response, but it's very thin as it is in terms of documentation and they also have hard-coded a redirected on their own for the sucess - not a full API like Auth.Net. But, still a good idea.
I originally was going to go with the database, as you mention - psudeo hash type of thing. There was then the question of abandoned forms and already completed forms and garbage collection along the way, so I thought that cookies would be a bit simpler.
What is going on is that I'm serializing the name values in the array and then feeding that to a single cookie per page after running that through a crypt function to encrypt the data. There are only 5 cookies total from the domain. I knew of the limitation of having a max of 20 per domain.
Lynne,
What browser were you using when your system crashed? Did you try to reproduce the error?
It wouldn't take too much more effort to drop a single pseudo-random hash (thanks for the term, Dmitriy!) as a cookie value and then store that serialized, encrypted array of data to the DB, but I think i'd like to try to increase the cookie size a bit and see if that takes care of things first.
Great suggestions, Dmitriy. As they say, 90% there, 90% to go!