Had this problem with my N2, N3 and now my N4. I can't use my bluetooth headset when the screen is locked. In order to use it I need to unlock the screen. This is a problem because I use my N4 with a bluetooth headset while I am driving very frequently. So having to pull over and unlock the phone while I am driving is not always possible and never very convenient. Have deactivated the lock screen feature but don't really feel safe doing that. Any suggestions on how if possible to get around the lock screen when making a call using bluetooth headset? Thanks for any help.