The first item to check is the encoding of the DAT file. In your favorite text editor, please check if the DAT is in ANSI or UTF8 format. If the DAT is not in ANSI or UTF8 format, please replace with an ANSI or UTF8 formatted version of the DAT.
The second check involves checking if the DAT has duplicated column names. Again in your favorite text editor, parse out the column header row and check if there are any duplicated column names.
Last check is if there are missing delimiters or malformed data in the DAT. This may require breaking the DAT up into pieces to find the malformed data in the DAT.