[ianhawes]

I've had a very similar instance.

USPS ShipNClick, for example, has "fraud detection" that freezes all accounts you've ever logged into if it detects that you've created multiple accounts and switched between them. And worse, it's a silent detection, so after you've entered all the details for your shipping label(s), it gives a "Your payment method was declined" error. No warnings or anything, just a vague error message.

When you call USPS online support, they're aware of the issue but they can't unfreeze accounts without "escalating" the issue. You get a callback in a few days saying that your account was "cleared".

[funkysquid]

I've gotten that exact error - good to know what was going on :P