I am having credit card rejection problems as well. My problem is only when I choose the alternate credit card number radio button; it displays the alternate address but in all capital letters (different from how I entered it and how it displays in the radio button displays). Then the credit card is rejected as invalid address.

I went bank to my bank's web site and erased the address and re-entered it; I did the same on my Delta profile. Same problem again.

I agree the web menu telling you what to do then is weak. It says to try again without telling you where to go on the website, or to call the general Delta number when you in fact need the web number to avoid the ticketing fee.