.key file is confirmed to be there.

Here is what it says in the watchdog:

Type uc_credit
Date Sunday, March 23, 2008 - 7:44pm
User Anonymous
Location http://example.com/order/cart/checkout/review
Referrer https://example.com/order/cart/checkout
Message Credit card encryption failed.

* No value has been supplied for decryption

Severity error
Hostname 65.89.141.30