There is no crop tool in PR CS5. There is a crop effect. Are you sure you are in the right forum?
Are you referring to the Crop Tool in Photoshop? If so, you have accidentally posted to the Premiere Pro CS5 forum. You want the Photoshop Fora. As Harm points out, there is no Crop Tool in PrPro, just the Crop Effect, which is added from the Effects Panel.
Oops, wrong forum.....
No problem. It happens all the time. I sometimes get confused which forum I am in, and will give PS "solutions" to someone using Premiere...
The regulars then have great sport at my expense.
Good luck with the Crop Tool. Other than going to the Tools Options area (usually at the top left of the Toolbar) and hitting Reset All Tools, I don't have much to offer.