It's a thought. I'll give it a try - I'd hate to have to lose the progress I've made on this guy after rewinding him post-1.10a problems. Thanks.
Update: I tried a TCP/IP game hosted by a character that had not done NM Baal (or any other NM quests for that matter) but the result was similar. After killing Baal, the quest log changed to "you cannot complete this quest because another character previously completed it".
I also noted that save files under 1.10s do not get the appropriate Mac D2 icons, retaining their generic icon.
Update: I tried a TCP/IP game hosted by a character that had not done NM Baal (or any other NM quests for that matter) but the result was similar. After killing Baal, the quest log changed to "you cannot complete this quest because another character previously completed it".
I also noted that save files under 1.10s do not get the appropriate Mac D2 icons, retaining their generic icon.