[Gretl-users] download/open problem on mac OS X 10.7.4

I' m having difficulty opening gretl on my mac air (OS X 10.7.4). I've downloaded gretl & unzipped it (and GTK as well) , open the gretl image, and get the gretl icon bouncing at the bottom of the screen...when I click on it, it disappears. What am I doing wrong? (By the way, I've had no trouble downloading gretl on my macbook pro (10.5.8), or on several versions of windows), Many thanks, Nick