I thought the same thing about the overlay file; it has a last edited date of 20 September 2010, so even though the error references it, I didn't think that could be the actual source. I do not recall making any code adjustments, no. Are there other files I could produce which you think could be related to this one that may not be working as designed?
Having reinstalled BAT a few times since the problem began, however, I did notice that I receive an error message at the start of the process which claims that my CIV IV: BTS version is not updated to 3.19. That confused me, because that is the version I have, yet I continued to receive the message when beginning the BAT install each time. I don't know if that issue is related or not, though.
Again, I appreciate the help - BAT really does make this great game even more awesome and I'm grateful for the assist on this problem.