Weird, idk I've always had a couple songs switched around. I really like cid's theme, i have it playing in limsa lol. Also i loved the theme they had for uldah what 8 months back? So i got that one back, and I like the old chocobo theme(like most) so i have that one swapped as well. I also receive this error every 4-5 updates(I received the error this time). And changing the version in the file fix's my issue. So I just assumed it was related to dat swapping.

Altho I will admit that I did restore my backup of the original dats and still had a error, but i did not delete the entire update and try to redownload/update.