Does anyone have any idea why every time I try to purchase a song on iTunes I consistently get a pop-up warning, which can be seen here:

For the life of me I can't make this warning go away once and for all!! And yes, I do have a valid credit card on file, and if I click on the 'Buy' button in the pop-up warning shown above, it does proceed to download the track...but trying to purchase multiple tracks back to back to back means that I have to click the 'Buy' button for each purchase!! It never used to be like this...

Anyone know how to stop this from happening so that clicking the 'buy' button simply begins downloading the track?

Any suggestions would be greatly appreciated... Thanks!