Scroll up the page a bit, the potential cause of that particular bug *MIGHT* have been identified and corrected. It's not a UOP issue though, it's definitely a vanilla issue that's not mod specific. Some crazy havok thing with loading cells and having objects that have rolled out of position causing their parent cells to fail to render properly.
There's a 4Shared link to a test file which you can try and then report back on, but it seems all but confirmed now that the issue is resolved there and in the other locations that are typically affected by it.
The community support for this game is still wonderful even after such long time.
I remember Kivan answering promptly to my every single query until he even confirmed a texture bug I noticed and fixed it in the UOP that was produced soon after.
I spent two evenings testing with the bug. On a vanilla Oblivion installation, patched 1.2 plus official plugins, the bug wouldn't happen. As soon as I installed the latest UOP I would get the missing chunk of land in the area I mentioned. After installing the UOP the bug would rear its ugly butt. I tried isolating the problem by selectively deleting the texture folder and the data folder, hoping for a nif or dds file to be the culprit, but to no avail. Deselecting the UOP esp in obmm was turning out to be the only (unapplicable!) way to fix the bug.
Well, I'm getting carried away already; thank you very much Arthmoor, I feel dumb I missed the post just a few above mine, but the esp you linked me to seems to solve the problem! I will test a bit further, but I'm quite sure it's working properly now. It remains a mistery to me why the UOP esp I was using would trigger the problem.
Thanks again for pointing this out to me, you've made my day. It now seems I can go back to the game!