My first response was to clean out your cache, and try it from another machine, as well as use the IE Private Browsing Session. The IE private browsing session did help resolve the problem, but this was not the solution.
In reviewing some issues further, we found a blog from Ben Klopfer about a similar issue. Ben reported the permanent fix is:
Log in to CRM as an administrator.
- Go to Settings > Administration.
- Click System Settings.
- On the “Customizations” tab, uncheck Load pages in the most recent version of Internet Explorer.
After making the change, Ben’s fix works great and the ribbon bar is now available. Ben’s original blog can be found here: http://thinketg.com/dynamics-crm-2011-ru-12-blank-ribbon-issue-resolution/. Thanks Ben!