Ok, this is what seems to be happening to most people getting this error. The authorization sent to my credit card was actually coming from the UK, so the credit card company flagged it as a security issue. After several attempts on 2 different cards, one of my credit card companies actually called me to confirm my recent activity.
Whether they call you or not, if you get this error you need to talk to someone at your credit card company (not the people at Click and Buy) and ask them to authorize the transaction. Once they disable the security flag, your transaction should go through. If it still isn't working, wait about 15 minutes and try again because sometimes it takes the system a few minutes to update.
Also, don't be freaked out if they tell you that Click and Buy is trying to authorize a transaction for $2.50. Companies like this have to send through an authorization to make sure your card is valid. An authorization is NOT a charge and will usually only hold for up to 7 days.