Dunc: I thought so too.
I think I know the answer.
Enlightened One had this issue and I helped him out. (he uses BL all the time, he used CE to only edit the weapons values)
I tried to re add the maps on my PC (cause he's stuck on a Mac) but I suffered the problem using a Vanilla exe (adding then with BL)
Anyway, I gave him the Sue's Story exe from version 0.1. and he didn't have the issue. (Yes, the most current version of Cavern Tale used the exe from Sue's Story)
I was a CE fan at the time and used it to make my maps until sometime after version 0.1.1 and then switched to BL after I had 112 maps.
I'm 90% sure that the issue of 102 maps is that using Bl to add the 102nd map causes the exe error.
Use CE to add maps up to 102, and then use Bl to fix the background errors.
My only problem with the theory, is the Magicdoors said that he has errors with the 102 maps and I'm not sure if that was before BL or not... (might have been related to SW though)
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Oh, and ANOTHER discovery, NPC 145 is King's sword.
This is why in the most current release of SS king's sword won't show up when he attacks Misery.
E: ninja'd