My guess is that the text is being interpreted as a date and the column width is too narrow. Try making the column wider and see if the ##### goes away. If it is being interpreted as a date, and you want to force it to text, place the ( ' ) character (unshifted quote key next to the Enter key) in front of the text.
If that isn't the problem, then select a cell that shows #####, then copy its contents from the formula bar at the top and paste it here in the forum so we can take a look at it.
The answer to why the text in the cell appeared as "####" when it did not exceed more than 250 characters appears to be that the cell must be formatted as Custom and the format is "#?/?". I don't quite understand why this is the case. It may have to do with the number of semi colons in the cell; there were quite a few. Thank you for your response.