Are you referencing a jquery lib that isn't marketo's or your own, like google's store of it? If so, set reference to marketo's store of jquery, as the jquery library has been updated and referencing the real most current version of jquery will now break some stuff, as in most of the calls that have been deprecated for the last few versions are now truly dead. One of those calls that I know was deprecated was browser.version, no idea if it is truly dead now in newest version, but the munchkin scripts use it and this seems a likely result of referencing the newest jquery library. Marketo has assured us that they will not update their version to one that would break anything.