Help Ringer Volume turning off at night

[Wizard832]

I'm having an issue with the volume on my Verizon Droid Pro turning its volume all the way down at night. This has caused me to miss several calls from family that were urgent and once to be late for work because I was using my phone as an alarm clock. I have checked all the settings i can find and can't figure it out.
Any help is appreciated.
Thanks
Wizard832