"FPS is low"

Towards the latter stages of a casual game - Fate's Carnival -I had this message when the game loaded, asking me if I wanted to turn off the special effects.
I didn't and it played fine but I wonder what the matter is. Mine is a new, fully specced, computer for adventure games.

I got this message during the game also and did not turn the special effects off and had no problems at all. I wouldn't worry about it. Having said that, I would be interested to know why we got this message in the first place.