I reset my HD2 and when I reactivated my WP7.8 started getting this error when trying to download from
the market place.
After a little google searching found a solution ......
had to go to Xbox live site (on the computer) and log in with the live id username and password that I
used on the phone to activate WP7.8 and let it make me a Xbox gamertag, during which process
it asked for my birthdate and country region, which was the info that couldn't be verified on the phone
when the error code kept popping up
once I finished that process on the xbox site ..... all is working and I can now download from the market
place without problem