If you have items in your cart, but are unable to proceed to the checkout page, please check to see if any of the products in your cart has three red asterisks next to the title. If so, you can remove the product and will be able to complete checkout. Then let us know the title and publisher so we can get the product working again.
If none of them have asterisks next to the title, you should be able to fix the issue by logging out and clearing your internet cookies and session data and restarting your internet browser. You can can clear your session cache and cookies in Firefox by going to the Tools menu > Clear Recent History and select either "cache" or "cookies." In Chrome, one clicks on the tools (wrench image) and selects Options, then clicks on "Clear Browsing Data" and selects "cache."
You should also check your system clock and if it isn't correct you will need to set it to the correct time and date.
Another possibility is that you could have an address mismatch. To check, please contact your credit card company to verify the address you have on file with them. Then log back in and go to your Account page (tab at the top) and then use the "Change My Address" tool and make sure that your current address with us exactly matches what your credit card company has. With any luck that will clear up your problem and will allow you to complete your transaction.
If you continue to run into problems you might want to try paying through PayPal. You can now use your credit card through PayPal without needing to have a PayPal account. PayPal seems to be able to accept a far wider variety of cards than we can directly.
Our system can occasionally have problems with very large orders as well. If you have a lot of products in your cart (more than 35), we suggest moving them over to your wishlist and then try checking out with fewer products n your cart, twenty or less at a time should work correctly.
If none of these help, please use the red Contact Us button at the bottom of each site page and let us know the titles/publishers for the products that you are trying to purchase and we can investigate further.