For the 3rd time I get in the night mothers coffin when the sanctuary is burning and it just stays on a black screen and all I hear is the fire burning. It never proceeds. And I'm stuck In there as well. Now I can't advance the DB questline. What do I do???

How long did you wait for? It's supposed to stay black for a bit of time.

If you wait it out it should be fine. It definitely stayed black longer than intended both times I did the quest (one time longer than the other), and UESP points it out as a glitch.

Maybe She wants someone to be close to, someone to make the day worth while. She needs you beside her forever don't ever leave her.
of course the sanctuary burning down s not the best time for this, tell her how you feel.

if that doesn't work you could always revert to a save. Perhaps a save before the one you reverting to currently.

Are you sure it's frozen? It takes a long time for the scene to move on. Creepy as hell, that quest.

I've only done it one one character, but, yeah, it seemed to take longer than I thought it should.

My PS3 lags for very long periods of time sometimes. I'll even push the PS button and nothing happens, but I'll set the controller down, walk away and when I come back 5-10 minutes later the PS3 T-Bar menu is up.

Exactly how long are you waiting?

Make sure you keep the door open for Cicero to walk through. That worked for me.

http://www.uesp.net/wiki/Skyrim:Whispers_in_the_Dark