Here is a tips which come from Total Video2Dvd Author website:

Q: When I add video files and message said not contain of the following characters and strings, how do i fix this?
A: As some of the reason that some characters can not be included in the file name(full name), double-check your file name, remove those who can not contain characters.

example: like "C:\\Video files\\1.avi", can not contain 'le'.