This came up on the mailing list a few weeks ago. If one tries to load the attached file as Intelligence, Bro will error out, with:
The attached file contains an extra tab after downloader.com.
It'd be nice if Bro would tell you that this was an issue with the input reader, which file it occurred in, and a line number.
I think generally speaking, if there's an issue with an input file, it'd be nice to know the line number.
(Also, there's a typo in mappimg in the error message that's currently displayed).