For anyone having this problem.....right click in the command line area and select options.
select the "profiles" tab
select the "AutoCAD" profile
select the "Set Current" button
select your previous profile or the correct one you really want current and close.
This should bring your "Ribbon" back.
Note: if you select the "Reset" button you will reset too many network configuration paths and this will give you a bigger headache than before unless your running a stand alone version of the software.
Let me know if this helps.
Thanks,
Johnny Mullins, IIDA
CAD Manager
http://jmblog.typepad.com/jms_blog/