Can't select space in spaces anymore

I've been using spaces ever since I bought my macbook pro and found it very useful. But after installing snow leopard, I haven't been able to use it properly. I currently have spaces enabled and have 2 spaces... when I activate spaces to show all spaces, I used to be able to switch between them by clicking on the space that I wanted to move to... however, I can't do that now. Every time I want to switch between the spaces, I also go back to the one I was already on.

Any ideas why this is happening?