I just got the 3GS maybe a month ago. Before that I had the original, and it never had this symptom. Basically, I will be sitting around doing nothing, and my phone will randomly vibrate once as if I have a text message. But when I check, there is no text message and none of my applications have a notification. Has anyone else seen this happening? I can't figure out what it is. It's like having a phone that cries wolf.