Double charge on Debit cards

We've been getting quite a few customers calling lately claiming to have been double charged on their debit card. When we check with our card processor, they say we only received the money one time. Our processor also says that this does happen occaisionally and the second charge should clear itself off of the cardholders account eventually (but they say it can take up to 30 days). It usually does go away after a few days, but it's still a hassle for our customers (one customer has had the double charge on her account for over

10 days now). The problem I'm running into is that it's happening much more frequently. We used to go months without having one. Lately we've been seeing it happen several times a week. It seems to be limited to debit card transactions. Also, lately we've seen a higher frequency of the first attempt to run the debit card not work, then the second time it goes through. We're not getting double money, but it seems like the customers card is reserving the money both times even though it's only approved one time. One thing one of the card companys noticed was the authorization number was exactly the same for both of the charges - seems a little odd. Also, our card company said the money we did get showed up as a credit card transaction, not a debit, which was how we processed it. We are running our debit cards directly through RMS on DSL. We've been doing it for over a year. Has anyone else seen this problem? Is it possible that our debit pin pad is going bad? Could their be another cause? I'm half tempted to stop using debit, but we're saving so much money using debit, it would be quite costly. Please share your thoughts.