When someone calls me I only get the vibration and no ring tone. Has this happened to anyone else??

I have checked that the phone is not on silent and have also checked that the ringing tone volume in the general profile is at maximum. I have also reinstalled PR1.2. The volume is fine when playing back music from the media player and even when selecting a ringtone, so the speakers still work

Does anyone have any bright ideas what might be the problem and any potential solutions?