I just got off the phone with GP support. Ok, this is the most idiotic security measure I've ever heard of. Like everyone else keeps saying, it's a safeguard for them to ensure that the person attempting the purchase is actually the owner of the account. Gotcha, and as much as I want to, I'm not going to rant and rave about how ridiculous this policy is. Essentially your account has been suspended by GP for 48 hours (I know the message says to re-attempt in 30 minutes, the GP support guy couldn't really explain this either). YOU CANNOT ATTEMPT ANY PURCHASES ON GOOGLE PLAY, WHATSOEVER, FOR 48 HOURS OR THE SUSPENSION WILL RESTART. So, unfortunately I've been attempting purchases over and over again for the last 3 days, based on the fact that that the error message says to retry in 30 minutes, so now that I have this information I have to wait 48 hours from the most recent purchase attempt before the suspension is lifted. Hopefully this clears things up.