Here's an issue I'va already fixed in my copy of morroblivion. Others might benefit from what I learned, so here's what happened.
I did a fresh install of oblivion, then re-downloaded everything for morroblivion and re-installed it too. I had some startup issues, but got everything fixed and so far it's working ok.
Here's the problem:
The Winged Twilight exists in 2 folders -
..\Creatures\WingedTwilight
..\Morroblivion\Creatures\Daedra\WingedTwilight
The esm points to ..\Morroblivion\Creatures\Daedra\WingedTwilight
But that nif is corrupted and causes ctd when you enter a cell that has a leveled list with winged twilight in it.
The old nif (skeleton.nif and body.nif) work fine, so I used them. I noted that the corrupted nifs are skeleton.nif and mesh.nif. I wonder why they're named differently? (*grin*) Anyway, I deleted those and my ctd went away (no longer happens)
I'm sure I installed something wrong, so if you have no problems then don't change anything.
ed:
I found a similar issue with the Hunger. I copied an original conversion hunger from the morro\creatures folder. It works ok.

Tested several dungeons,
Tested several dungeons, wandered thru the ashlands, visited several caves. No crashes anywhere.
Here's a question for David:
I know you told me the Golden Saint comes from SI, but are there any other creatures that are from SI? I've found and fixed WingedTwilight, Hunger, and Golden Saint. Those three creatures appear to be what's been causing most of my issues.
Also, why does the The Winged Twilight exist in 2 folders? Maybe a folder left over from the original conversion?