Insert cells may not work even if you use the option by right clicking in the sheet of from the tabs.
To make it work there are two methods here. You can try any one of them
1) Application method
Close all the instances of Excel
go to %appdata%\Microsoft\Excel
In My case it opened C:\Users\yummyrecepiess.oneshot.in\AppData\Roaming\Microsoft\Excel
Find a file Excel14.xlb or Excel15.xlb.
My case it was Excel14.xlb
Just remane the file to Excel14.old
Bingo..Start the excel it works
2) Regestry edit method
Close all the instances of Excel
Open registrt editor by typing regedit in the command prompt
Find the key “\Office\15.0\Excel\Options”
Delete the key
open and see the excel it should work