AbleCommerce Shopping Cart Software

I have just had my first few transactions of a new site. My gateway setting is set to Authorize Only. The transactions go over to authorize.net as "authorize only" and they are saying that they can not settle those transactions unless I change my gateway setting to Authorize & Capture.......so, what am I doing wrong?

You're not really doing anything "wrong". Charge card companies don't want you to capture until the order ships. I think you have to do that from the authorizenet admin, but I could be wrong.

You haven't "captured" your payments, so there is nothing to settle.

Either set your payment gateway to "Authorize & Capture" or pull up the payment for each order and select "Capture Payment" from the payment action menu.

Authorize.net only settles captured payments because funds have actually changed hands. Authorizations are just a way to reserve the right to transfer funds at a later date.