I have never had so many weird experiences in Oblivion as in my current game. I don't recall all of them but yesterday was the strangest of all. I had just left Umbarcano after talking about the High Fane and followed the Breton Claude Maric into the Tibor Septim for a drink, but when we got inside, all hell had broken loose. Everyone was fighting with a goblin, watched by a horse standing in the corner by the bar. The fight moved outside so I followed them and killed the goblin, then went back in to meet Maric, but he wasn't there. The horse was still standing there in the corner. The next time I slept, I was visited by Lucien LaChance, although I don't think I murdered anyone. Did Marec change into a goblin?
Several times in this game people I was supposed to talk to about a quest weren't there although the green arrow showed they were. I finally found that if I moved around where the arrow placed them, the symbol appeared that allowed me to activate a conversation and they became visible.

The Tiber Septim is known for strange stuff to happen. It is the "fallback" cell that the engine uses to drop every creature whose original position couldn't be found (for example because the mod was uninstalled).