Using the default size can sometimes lead to the "unexpected end of file" error message. This is most common with the money and datetime datatypes.
The error occurs when only a fraction of the entire date (for example, mm/dd/yy with no time) is used instead of the entire date string. When using the default size option, SQL Server expects to read 25 characters (the length of the date type). To avoid this problem, read in data using delimiters, or create a user-defined fixed-length ASCII file for reading in data.