Added an extra try block to handle FF 3 x-domain requests. (Bug #1557)

src/ajax.js

@@ -255,6 +255,8 @@ jQuery.extend({
 		// Open the socket
 		xml.open(s.type, s.url, s.async);
 
+		// Need an extra try/catch for cross domain requests in Firefox 3
+		try {
 			// Set the correct header, if data is being sent
 			if ( s.data )
 				xml.setRequestHeader("Content-Type", s.contentType);
@@ -266,6 +268,7 @@ jQuery.extend({
 
 			// Set header so the called script knows that it's an XMLHttpRequest
 			xml.setRequestHeader("X-Requested-With", "XMLHttpRequest");
+		} catch(e){}
 
 		// Allow custom headers/mimetypes
 		if ( s.beforeSend )