i am on my second time through oblivion having finished the game of the year version 3 months ago.
i found the first play through just like reading a raymond.e.feist book. i just couldnt wait to see what would happen next. so i didnt do a lot of side quests only the guilds and main quest.
this second time round however i have gone out of my way to complete all the daedric quests. all has gone great i have done all but one with out a thing going wrong. i even managed to get through the clavicus vile quest without encountering the bug.
then i was sent on the heaceus mora to soul trap one of each race. i soul trapped a dunmer then an argonian.
figuring all was well i saved well after the encounter with mora.....BIG MISTAKE!!
i then went to soul trap one of my fellow kajiit's and found mora's soul trap spell no longer works. the magic still shoots from my hand but the target no longer flashes purple.
now i have saved so far in the progress of the quest there is no going back and im soooooo pissed.
i just thought id warn others of the potential bug and advise u keep a back up save from the start of all daedric quests as well as your progressive save.
from what i have read in forums these are the quests that have the most bugs.
happy gaming ppl!!!!!