Cross reference these posts:
As stated in the title, at some point when playing Morroblivion, actors which turned hostile for any reason (whether by beng attacked or being enemies that detected me, would freeze in place and not move towards me. They would still case magic, shoot arrows, and swing at me if I came in melee range.
The above posts suggested that some script was causing the issue. I discovered that if if removed OBSE from my Oblivion folder, this glitch went away. However, Morroblivion depends on OBSE.
After hours of editing Morrowing_ob.esm and deleting random scripts, I finally determined which script (at least for me) was causing the issue:
Using TESIVEdit, open "morrowind_ob.esm" and go to "script". Scroll through all scripts to "0101E4CD fbmwBMMissionaryScript". Right click it and in the context menu that appears, click "Remove". Wait for the "warning" timer to expire, and then click "yes". Close TESIVEdit, and it will save morrowind_ob.esm.
Now you should be good to go. Hostile actors can move again.