The same happened to me. It is quite easy to fix:Hey.
My moms Incredible S got this weird issue that came after updating, first of all its not rootet.
The problem is that she gets SMS's constantly from the number: 50, when ever the connects to another teletower (I dont know the english word for this?), and its not a normal text, it comes in a pop-up, and she got the option to save it as a sms or cancel it.
Anybody knows what the problem is?