Limitup, honestly, I donít think what you've experienced is connected in any way with your card having been declined. I'm not aware of any changes that kick in when a card is re-entered, or the need to recalculate CTRs, CPCs, etc. So I'm a bit curious as to what Wired Suzanne has seen in the past.
I could see raised CPCs, I suppose, if the card was declined and then not re-entered for an extended period of time - during which time the competitive landscape may have changed.
I guess my best advice would be to contact AdWords support and let them have a crack at answering your question. A look at the account would probably help, I think.
Off Topic Note: I've mentioned recently that I have had less time to post here - and I'll actually be away from the office tomorrow, Friday, through Tuesday. I'll almost certainly not be posting to WebmasterWorld during that time. I've been called to task a time or two recently for not responding, so wanted to give everyone a heads-up in advance.
So, if I'm asked a question between this evening and Wednesday, and I don't respond, well, I'm not ignoring the question. I'm just not present and accounted for. ;)