I just updated from version 0.27 to 0.32. I made sure to download Additional Files 1 and 2, Eloth's Miscellaneous Items & Ingredients, Henshu Lute music, and the version 0.32 Masterfile installer.
I loaded my game, and everything was going fine. I was inside Arkngthand, doing the Antabolis Informant quest (http://www.uesp.net/wiki/Morrowind:Antabolis_Informant). The cube hasn't appeared, but I believe this is simply due to the fact that I may not have progressed far enough to trigger the script that causes it to spawn.
Anyway, I exit the ruins, and immediately fall into water, hundreds/thousands of feet below. I tried fast travelling back to the ruins, but fell through yet again. I can see such things as peaks and other objects (such as the entrance to the ruins).
I tried travelling to Balmora. Thankfully, there is still some ground, however, entire cells (I think they're cells) seem to have completely vanished; the ground as well as the buildings that rested on them. As I walked by such a hole, I could vaguely make out the outline of a building, but just barely. Balmora's temple is floating in mid-air, and I keep seeing/hearing NPC's falling into the water. I saw two NPC's exit the temple and fall.
Any ideas as to what the cause might be?
#1
"Morrowind_ob.esm" NEEDS to load directly after "Oblivion.esm". If you've got it any further down in your load order, this will happen. Check in Oblivion Mod Manager.
Note that, yes, updating Morroblivion will break your previously assigned load order.