I can't complete this quest. I get as far as being transported to the sky to speak with Meridia, but when she sends me down, I get stuck and can't move, or I hit the ground and die. I'm running a few mods, but none that effect any quest afaik. Has anyone else had this problem? How can I fix it?
It's not listed under the glitches section in UESP.

I have the 360 version and occasionally have this problem too. If that glitch happens, I usually just reload a save I made before talking to Meridia and keep trying until it works.

Make sure you're not over-encumbered.

Since you're on PC, just before you pick up Dawnbreaker open http://www.uesp.net/wiki/Skyrim:Console and enter the command

tgm

and hit Enter. This Toggles God Mode, so you can't be killed. Close the console and collect the prize.

After Meridias' speech and you return/fall back to earth, enter the same command to turn god mode off.

Yeah I was getting problems earlier and was doing this, but the same thing has happened about 6 times by now
Definitely not over Encumbered. I'm getting weird lighting from the ENB I'm using as well so I'm certain this is a glitch.
I should clarify that I'm having problems before I even get into Kilkreath Temple. This is when Meridia sends you up the first time.

Then you can enable god mode before you place the beacon, and turn it off before you enter the temple.

The culprit may be a mod that was removed during the life of the character. I was using the Saved Games from Steam Cloud on my at work laptop, when Meridia lifts my character after placing the Beacon, my character would not get the chance to talk to her and was instantly sent back down.
I am bringing this up because after my character kills Malkoran, they were teleported to the sky and were left standing there.
The tgm works for not going splat when being accidentally dropped.
I did get my at work character to work correctly by reinstalling the mods that my at work PC does not normally use.

That's interesting, because mods I've removed have caused problems with bloating on this character, but nothing getting in the way of quests. I'll keep that in mind.

EDIT: I just tried it again and I got transported down safely, I'll keep the thread updated if I have anymore issues.