did you have express email with the blackjack? i also had the blackjack before the iphone and are receiving this weird text as well. I used to get the email pushed to my blackjack shortly after it was received, and then i was sitting at my laptop and got an email, then shortly thereafter received the weird text. I think its the push client trying to send an email that isn't compatible with the iphone.
If this is so, turn off the Xpress mail professional and then that should stop the text...