senbon: What part of the 'main quest' are you (maybe a quest is locking other quests out)?
Have you tried to burn in after meditating?
Have you tried to load an earlier save just to check if there is any difference (by trying to burn that body first)?
Yes, I have tried to burn it after mediation. Didn't work. it's just one body that has this nonburned look. I have tried casting Igni directly on the body and throwing a bomb at it. Didn't work.
An earlier save seemed to burn the body, but I don't want to go all the way back to the beginning.
Xealot42: I've noticed that even if you burn the bodies, when you leave the area they will revert to their non-burned look but you can't burn them again.
I would visit each of the three sites and double check the three bodies at each to make sure you didn't miss one.
I will visit each of the 3 sites again to double check each of the 3 bodies and see if that works.