The Snapshot feature of Camera Raw is only in version 5.2 or above...sorry, won't work in Photoshop CS3, you need CS4.
…My latest download of CS3 was in Jenuary, so I got 5.6, right, …?
No, you actually got Camera Raw 4.0, which you now need to update to 4.6, the last version to run in CS3.
As Mr. Schewe points out, that still won't give you Snapshots. For that you would need CS4.