jQuery's $.ajax URL Encoding Problems
You can use javascript's encodeURI() function to encode a URL into "Firefox format" as you state.
Passing [Product Type B] in unencoded form is invalid, so what the browsers make of it is undefined.
Do a encodeURIComponent() on the product type part.
I think .serialize() would be the jquery way to do this.
check here: http://api.jquery.com/serialize/
also there is a plugin for jquery: http://plugins.jquery.com/project/URLEncode
or the javascript way ... encodeURIComponent()
check here:http://www.w3schools.com/jsref/jsref_encodeURI.asp