The unknown (well at least to me) limit is based on the amount of data, not the number of rows. So it will depend on the # of columns and the amount of data in each column (sort of the field width as to a lot or a little text).
I suggest that you cut the # of rows in half and try again and it will likely work unless you have a ginormous number of columns.
Basically its trial and error to see what amount of data it will take.