Fixed #1557, although it doesn't appear to be just an FF3 problem. In this case, $.getJSON() wasn't working from a remote host. I went ahead and added a unit test then added the s.dataType == "json" test for a remote <script> load. The said that json was allowed but the dataType check was missing. This appears to have fixed the bug across all browsers.

test/data/json_assigned_obj.js

@@ -0,0 +1 @@
+json_assigned_obj = { "test" : "worked" };