excel 2007 all commands/tabs disabled

I have a file that I have come across. It has a peculiarity that i have not been able to explain.

When the file is opened in excel 2007,all tabs and commands are disabled/gray开发者_Python百科ed out. Even the protect/un-protect commands in the review tab are disabled. the file does not for a password on opening and does not contain any macros. This does not happen with any other file that I attempt to open. Can someone give me a lead as to what might be happening?

I figured it out. If you press "Mark as Final" (Office button > prepare >mark as final), all commands and tabs are grayed out and disabled. There is an icon showing this on the status bar as well ( which I didn't notice earlier).

Clicking this combination again enables all relevant tabs.