Dell Venue Pro with Windows 7.8 not ringing with new incoming calls

I have a Dell venue Pro that I have updated to Windows 7.8-- not sure if this is a factor in the problem I am having

The DVP does not ring when a new call comes in but if I plug in the head jack into the antenna/call jack I can hear it ring most of the time but sometimes I just here a little sound than nothing. I set the phone back to default factory settings. I have found a couple of post on this subject but no solutions were provided.

Thanks for your help

Mark