After weeks of more or less peaceful gameplay, I entered an area of intense fighting which turned out to be also prone to crashes.
The area in question was the underground city from the Vampire questline in Origin of the Mages Guild. The crashes are apparently the result of that mod combined with StarX Vanilla Vampire Revisited and possibly other mods on my list. That is not to say Origin of the Mages Guild caused the crashes – I know better than that. It could be very well other mods in my list causing a crash in that area.
Anyway – one particular side effect was to encounter, twice, a situation where the game would systematically crash. In one case, any past saved game related to the underground city would crash on load (although they were loading fine a minute before). In another case, I would get a crash each time a Vampire Warrior was killed (but not the other kinds of foes I would find).
Both situations are highly unusual in terms of Oblivion bugs.
What I believe happened is that repeated crashes left some textures or mesh files locked by the operating system (Windows XP in my case) and caused a crash next time the game tried to load these resources.
So if you are running into a severe crash in the game after a series of smaller crashes to desktop while you play – calm down, shutdown your computer and reload the game after a while. Chances are your crash will go away.