Help please...mesh tool in Illustrator is killing me

Hi Guys

I have been trying to do what this guy does on the video

‪Adobe Illustrator CS4 Gradient Mesh Tool Tutorial‬‏ - YouTube

I make a circle shape, fill it with a colour. Type a letter s, place it over the circle, find the outlines of the type and then use pathfinder to subtract the S from the circle to leave me with a yin yang sign. He then applies a mesh to one side of the yin yang and then the other, yet when I go to do it, it wont let me add a mess.

Please help, it's obvious it can be done because he does it in the what am I doing wrong? I've even tried expanded the yin yang shape after but thats changes nothing :)
What happens when you click on the shape with the mesh tool active? Does it give an error of any kind?

If you try selecting the shapes with the direct select tool (A) is the mesh visible then? I've just tried the steps you described at I'm able to use the tool without problem.