3.5.0.x Reserve your site button fails to work as expected

I've tried all the different versions of 3.5.0.x but every minor upgrade does not work as expected.

In 3.5.x.x versions from 3.5 to, the "Reserve your site" button does not work. Nothing happens when clicking the button. Thus I had to disable checkout and use WordPress checkout instead.

However, while creating new user+new site works, when the user logs in, he is unable to create multiple sites as the "Reserve your site" fails to fire the ajax code.

Unfortunately, my javascript debugger does not fire any errors except that it cannot resolve $('#gateways').tabs().

There is currently no remedy for this. Therefore, the only way to solve the issue has been to roll back to

I would like to use the latest version, but this and many other issues that I see being reported on 3.5.0.x does not help the situation.