I came across two naked NPCs after installing Oscuro’s Oblivion Overhaul. One was a blacksmith in Anvil and the other was in the Fighter Guild in Skingrad.
After troubleshooting the issue for a while, it seems that, quite simply, OOO doesn’t check if a NPCs have any kind of clothing before removing their armor when they sleep/wake up.
In the case of Fadus Calidus in Skingrad, that NPC doesn’t have clothing under his armor to begin with (vanilla oblivion), so he ends up naed when OOO disrobes him.
In the case of Varel Morvayn in Anvil, Blackmagic’s Rogue Set replaces his clothing by an armor set, instead of adding the set to his list. So then again, if that mod is loaded after OOO, the blackmisth ends up naked.
Unless OOO adds a check for available clothing before changing what they wear, you can expect to see a few more naked NPCs eventually. I ended up creating a small .esp that restores the NPCs clothing and included it in the bashed patch. Works like a charm.
For more on this issue :
[REL] Oscuro’s Oblivion Overhaul 1.32 RC2 – Bethesda Game Studios Forums