If url given to $.get() already contains GET parameters and additional params hash is given the request querystring will be broken.

var get = {"xxx" : "yyy"};
var url = "http://www.example.com/test.php?foo=bar";
$.get(url, get, function(f) { 
    console.log(f);
});

/* Resulting url:                                  */
/* http://www.example.com/test.php?foo=bar?xxx=yyy */

Live example at:

http://www.appelsiini.net/~tuupola/test/jquery/get_querystring.html