I've done a little research on that error, seems like it's related to the PSN account that you are using, something about multiple devices under the same PSN account, maybe you can try to sign up for a new psn account afresh and then reformat your vita and try my method again, make sure to link the new psn account when first iniating your vita after the format, if it doesn't work then I have no clue, sorry.
If you are activated and did the adrenaline installation, did you apply the psp mini adrenaline fix? That error happens if you use psp mini game as a base, which epsp 2.0 installer uses, so you need a fix:
http://www.mediafire.com/?tk1f9u96lzkthno