I have an iphone 4 with IOS 4.0.1 - jailbroken and unlocked. Just recently, every time i receive an SMS (text) message my phone does its usual ring and single vibration... well now, after the initial ring/vibration - when i slide to read the message, i hear the outgoing sms sound as well as another single vibration.... why is this so??? i've done all the resets and googled but cannot find anyone who has reported the same problem. I dont want to contact apple yet if possible. I've played with all the alert settings and what not, upon a reset done from the settings menu - the problem ceased momentarily, then started up again...

any advice??

oh and it doesn't happen on ALL text messages.... only on occasion... ODD!!