NewDroid4

Hi All,
I have a new Droid 4. It recently automatically upgraded to ICS. I dont have any special mods or non-standard apps, including messenger apps. I have not rooted the phone.

The phone's default behavior is to play a ring tone and vibrate when it receives a text message. I would like to change this to just vibrate, no ring tone. I want this only for text messages; i dont want to change into silent mode or anything else global like that.

In the phone, i tap the "Text" icon (green text happy face), which expands to "Text Messaging.
I then tap the 3 lines button at the bottom left, which pops up a little dialogue that has "Messaging settings" and "To Online Album". I tap Messaging Settings and get a new screen with lots of options.

I scroll down to the "Notifications Settings" section. In there, there are 3 subitems: Notifications (Checked), Select Ringtone (default ringtone, droid), and Vibrate (also vibrate when notified) which is checked.

I tried setting the ringtone to "Silent" and making sure that vibrate was still checked. But when I got a new text, it didnt vibrate. There was indeed a notification in the notifcation area at the top of the screen, but the phone made no noise (as expected) and did not vibrate (not expected).

Am I doing something wrong? Is this a known bug?

What can I try to do to get the behavior I want?

Thanks.