LRC Stacking

Hi 

Why is the stacking not working? I select all the shots by selecting the first shot, then pressing the shift key after selecting the last shot in the series to highlight all the shots I want to stack. I then press ctrl+G and nothing happens and also all the stacking options are ghosted out in the "Photo"  Stacking Options.

Frankly, I find this programme is too up itself to achieve the same results that I can get so easily in Bridge/Raw/Photoshop.    

If anyone can point me in the right direction or show me the error of my ways it would be highly appreciated.

Thanks

Derek Salter