I just upgraded bootstrap from 2.0 beta to 2.1 and my drop down menus, which were working fine, no longer show up.
There were a lot of changes made in the 2.0 release and moving forward, you'll have to be more specific: Please take a look at https://drupal.org/node/1998352 and see if you can pin point the issue that may have caused your menus to not work.
Figured it out. After upgrading to 2.1 the CDN setting was disabled in the theme's setting page. Turned on the CDN and all worked like a charm.
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