Can't cycle through tabs since 3.5

Since updating to WordPress 3.5 you now can’t get to the Add Existing Users/Create Blogs tabs. It’s giving a JS error:

Uncaught Error: cannot call methods on progressbar prior to initialization; attempted to call method ‘value’ load-scripts.php:2

v.extend.error load-scripts.php:2

(anonymous function) load-scripts.php:13

v.extend.each load-scripts.php:2

v.fn.v.each load-scripts.php:2

e.fn.(anonymous function) load-scripts.php:13

resetProgressDialog users.php:625

handleSelection users.php:632

(anonymous function) users.php:863

l load-scripts.php:2

c.fireWith load-scripts.php:2

v.extend.ready load-scripts.php:2

A load-scripts.php:2