Checkout loop?

[BDog21]

i read through a few of them but almost all of them are only about when checking out with paypal, im not using paypal and the only time it happens is when i try paying with a visa or mc...if i install the free shipping module and checkout using that it works fine, but when i try to use a card it takes me back to login

[dbltoe]

Please hit reply and answer all the questions you can from the posting tips.