Beer generally comes in 6-packs and 12-packs (and here in Canada in 24-packs, but that's apparently just a Canadian thing). By "case" it sounds more like a 12-pack, but it could just as easily be a 6-pack, since in some areas that's the only size of case that's sold.
Basically, it depends.
The word "case" doesn't imply a number, just a method of packaging. While generally speaking, a case is thought of as holding four six-packs, or 24 bottles or cans
Here ya go:
http://www.answerbag.com/q_view/11048