I noticed that when using an expired/maxed out/otherwise invalid credit card number and get the message "unable to authorize your card' and to enter new card info that means my bid was accepted (otherwise it says 'we can't accept your bid'). That means I can then open another window and rebid (using free rebid or whatever other strategy) and try for a lower rate (starting from scratch each time not using 'try again' option). Once all my bids are used up (assuming they aren't successful) I can then go back to the payment window and secure that bid. This has worked successfully every time; even waiting several hours to fill in 'real' payment info.

Since there's a lot of bid-savvy people in the forum I apologize if this is nothing new but I didn't see it mentioned on the first few pages when I searched for Priceline.