Undo not working on 2.74 my undo does not work on 2.74, but it does work perfectly on 2.73 and older.
If I change keymapping from ctrl + z to something else, it still doesn't work.

Operating system is Win 7

Thank you for you help!

Tapio
You probably have set the undo steps to Zero in the User Preferences :

go to : User Preferences➜Editing➜ Undo➜ Steps  and set it to some number ( default 32 ) then save the settings