Don't blame mods too quickly, Cautionary tale
So I was tweaking with updates, still waiting for the final releases of OOO and MMM (are we there yet ? ).
I thought I had everything up to date, clean load order and brand new game.
And then... suddenly ... the Spell Effect replacer bug started getting out of control, I could not summon a skeleton without having it collapse immediately into a heap of bones and after walking to a new cell ... crash. Repeatedly.
After testing and testing again, I came to think the culprit was Reneer's Guard Overhaul and disabled it.
Only to find out that the real culprit was.... OBSE v11. I had updated Supreme Magicka and did not read the readme file closely enough, so I missed the requirement for OBSE v12.
So the culprit was really just me... now Reneer's Guards are happily back in my game and I can summon skeleton's again, so I can go back to ... waiting for OOO and MMM
End of the story.