I think the $.ajax override is causing problems with jQuery 1.5 -- calls to $.ajax with dataType: 'json' are triggering JSONP requests instead.
Reported by another user here: http://forum.jquery.com/topic/getjson-and-jquery-1-5
Thanks for the patch.
FYI there is also a patched fork for jQuery 1.5 written by the guy who re-wrote AJAX for 1.5 here:
"Fixes jQuery 1.5- code by using jQuery.ajaxSettings and not window.ajaxSettings (yeah, that was dumb)."
I'd love it if you could pull the fix from https://github.com/jaubourg/jquery-validation or adapt it. Even documenting on http://plugins.jquery.com/project/validate that the current version is incompatible with jquery 1.5 would make a difference to us poor newbies.
Thanks for the handy tool.
Pulled in jaubourg's fix.