I thought so, I didn't think the 14 day block was the cause. I knew what the block was like. They wouldn't even allow you to put credit card detail with Alaska and US airways.
Another conspiracy theory I came across is that you need a US billing address, but it seems like everyone here is OK, so that's not it...
So I seem to be the only one with the problem? Bummer! Why?
I think the 14 day rule is a fairly recent one introduced on promos. Someone can vouch or otherwise for this. (Wouldn't really affect me as I've had my AAccount open for yonks before buying AA miles became fashionable).
I've had no problems using my credit cards to purchase miles from US DM, AA, SPG and IHG (nee Priority Club) - all use the points.com portal. I do tend to call my credit card providers in advance and tell them that a (or a few) big transaction(s) are coming my way (for a particular ballpark amount); usually only the first time when I've done that kind of transaction or where I haven't done such a transaction within 6-9 months, and if the transaction is time critical (i.e. to make the deadline of a promotion). I usually don't call them now because at least my main card has been through enough of this it should be nothing unusual.
As for billing address differences, can't comment on that, but mine have always worked. I tend to use the one street address line, city, state (where provided), country and zip/postcode; this works fine. (There are some "tricks" you need on AA's booking engine but not purchasing points, as it were). I also have a PO box address which I use from time to time. For example, my address would be entered:
Street Address: 29 Anatol Drive
City: Frequent Heights
State: QLD (or Queensland if available via drop-down box)
Zip/Postcode: 4999
I know some people put the suburb as the second line of address and the city as "Brisbane" or "Sydney" or whatever; in reality it shouldn't make a difference except I guess that may throw up some automatic systems when data matching (if that is exactly what happens).
For phone number, I use my mobile written in proper international dialling format, i.e. 61401234567
I am rather surprised that you had at least two cards declined to follow through with this transaction. I'd like to think it was something other than the cards rather than the cards themselves, though; however, you did say that the accounts were of the correct age.