This issue can come up when trying to update on the kindle itself, which often doesn't relay the info back to amazon properly.
There are a few easy steps to fix this though.
First, on your computer go to amazon.com, click on YourAccount at the top right of the page, log into your account, then go here:
• Manage Payment Options
there you can be sure your card/bank info is correct (right address, valid expiration date, etc)
From there, go here:
• Manage Your Content and Devices
On this page, click on the SETTINGS tab at the top right,
then you can from there set a default card to be used for one click purchases on the kindle.
Under Kindle Payment Settings, click on the Edit Payment Method button, and you can set the card you want used for your kindle purchases.
After that, reboot the kindle by pressing/sliding and holding the power button for 20+ seconds, and it should operate normally from there.