OK, the Station Exchange team has looked into all of this and provided the
following response (copied from link so you don't have to follow it):
In order to help accomplish our goal of providing a secure service to our customers, we have enabled tighter security checks in the Station Exchange system. This change has altered the way customers use the system and we apologize for any inconvenience this may cause. The best course of action for anyone having difficulty using Station Exchange after this change is to confirm that all of your personal information is as accurate as possible. We are closely monitoring the system and still investigating ways to resolve any issues our customers are having as a result of this change while striving to provide a more secure service.
What's that mean in English?
We have tightened up our controls during the transaction to make sure everyone is using a valid card. They are casting a wider security net as an analogy. For the bad people who try to work bad information through the system this ensures that they can't. Unfortunately a few good people are being caught in the net.
So, nothing is broken, but they are monitoring the changes and the issues you guys are bringing to CS and looking for ways to tweak the system so it does not snag you on accident.
But I've been caught up in this net, what do I do?
Get a /petition in, work with CS. Yes, I know that it stinks for anyone who's in the situation, but we need those tickets in CS to identify common trends and issues that the team can look into. Unfortunately, because there are people out there who want to try to work the system with bad information, we need to tighten our security checks to make sure that the person winning your auction is actually going to provide you the funds for the auction.
Thank you for your patience while the Station Exchange team looked into everything. I know it's been a bit of time to get to this answer but they wanted to make very sure that there wasn't anything broken in the process when the security system was turned up before they gave a clear answer.
LINK