Currently Being ModeratedMay 29, 2012 4:11 PM (in response to BobKier)
You need to select (highlight) the item first.
And you can't do that on a Local Snapshot (gray "tick mark" in the timeline), only an actual backup on an external HD, Time Capsule, etc. (purple "tick mark").
Then you should get the Delete All Backups of <item> option.