I am wondering that too, I was going to buy magic the gathering but all my ps cards are giving me that error..
I guess ill just wait...
UPDATE: I found the cause of the problem updating my credit card information solved the problem the 3 digit security number was missing off my account, what this has to do with playstation network cards dunno, but a incomplete accout information seems to cause the error.
I had partially changed my account when putting in another credit card but stopped yet never corrected the information.
So thats it make sure your credit card information is current and accurate and it should let you continue to redeam your psn network card.
I received this error code twice with PSN Cards. At first I thought it was my system. Then I thought about the store I purchased it from. I called them and told them I just purchased two PSN Cards and neither work. The guy remembered me (regular at this store), he told me to bring the cards back to him. He gave me two new PSN Cards. Yes, these two worked. It's not your system, it's the card itself. The PSN Card probably didn't register correctly at the store you purchased it from. In any case such as PSN Cards always keep the receipt. If, it doesn't work return the card back to the store. It probably didn't register correctly.
yah...i just bought a PSN card to get $20 so i can buy some stuff...i know the code is right because i tripple checked and it said "add $20.00 to your wallet?" so i KNOW its not the card...maybe it has to do with net trafic...like alot of people using your internet or alot of people trying to add funds all at once (like when a big game comes out)