"All" as in multiple?
Available credit works against you as well for loans even when it is balance zero, so if you have multiple cards all with plenty of available credit (but yeah, zero balance) that can actually be a negative so far as loan approvals go.
Banks are all about risk, and when they determine that a wrong turn of events could have you unable to pay your bills (and then maxing out all available credit and making it even worse) they are generally not very willing to extend another potential bill to you if they determine you're already on the bleeding edge. Add a few credit dents into that mix and you're toast.
edit: Looks like we were replying at the same time, strictlye on the same page.
