Driving Mode isn't working as expected on Samsung Galaxy SII

I have this Samsung Galaxy SII, GT-I9100T, with Android version 2.3.3. When placed in Dock with my car, the following happens - Whenever a call is incoming, the phone would read me the calling number, even if he's found in my contacts. - Whenever a message is incoming, the phone will **sometimes** read me their phone number, even if they're found in my contacts. What can cause this? I've checked the configuration and found nothing helpful, Google wasn't much of a help either.