It seems as if the save file you have isn't encrypted/signed properly. This can be done with my save resigner tutorial.
The tutorial is over in the how to and guides section called the Ultimate PS3 Save Resigning Guide. It will show you how to sign the file and how to get the file id.
If you sign it properly and it still doesn't work, I highly recommend making sure your using the same account. Otherwise you may need to change the account id inside the PARAM to ensure that its tied to YOUR account.
Basically, grab a PARAM from another game using the same account and open it in the save resigner and save as Profile X (X corresponding to the number slot you want to use)