I got a credit card which gives me extra points for buying at office supply stores. The mystery is my credit card swipes just fine at any other BUT office supply stores, where they have to enter the information manually; and a lot of times, the cashier has to call the manager to do this. I often buy gift cards at office supply stores; is there anyway my card has been "marked" in some way by these stores and stop it from working in their readers? I just don't understand why I ONLY have this problem at office supply stores. Does anybody else have this problem?? Thanks!