Excel not playing cricket

[Mattyads2011]

For some reason when i enter a very simple Cell reference formula =Sheet1!C6
Excel is displaying the formula rather than the result. To confuse matters more, i could try a slightly different, but same function, formula in the cell above and it works fine. Can anyone please explain why this is happening?

 

[CharlesChuckieCharles]

Is your calculate on Manual?

 

[GlennUK]

What happens if you type just the = and then navigate to the data cell and press Enter?