I've attempted several times to purchase Dead or Alive 5 Plus via my PS Vita. Upon each attempt to add funds to my wallet using the same card I've been using on PSN for years, I get "An error has occurred. (E-80551071)".
I've also attempted to add multiple times to add money using "Wallet" tab in the Account Management tools online with my laptop. On there I received the message "The credit card information is not valid. Please check your entries carefully." This is after the information was successfully saved under "Billing" tab. The information has been double and triple checked, with NO ERRORS.
It's frustrating enough to have a limited number of games I even like for selection on the PS Vita, but to not be able to conveniently purchase them adds insult to injury, especially knowing that I purchased the Vita when it first came out.
Seems someone else had the same issue here: http://community.eu.playstation.com/t5/PlayStation
If you can't get it sorted out I also recommened contacting support here: http://us.playstation.com/support/contact_options/
Good luck with your issue!