Did you really mean textboxes or cells on a worksheet?
If you meant cells in a worksheet...
It could mean a few things.
1. The columnwidth is too narrow to show the number.
2. You have a date/time in that cell and it's negative
3. You have a lot of text in the cell, the cell is formatted as Text.
4. You really have ###'s in that cell.
5. You have # in a cell, but it's format is set to Fill.
To fix #1: Widen the column or change the font size of that cell
To fix #2: Don't use negative dates. If excel was helping you, it may have
changed the format to a date. Change it back to General (or some
other number format).
If you need to see negative date/times:
Tools|options|Calculation Tab|and check 1904 date system
(but this can cause trouble--watch what happens to your dates
and watch what happens when you copy|paste dates to a different
workbook that doesn't use this setting)
To fix #3: Format the cell as general.
To fix #4: Clean up that cell.
To fix #5: Change the format
(format|cells|alignment tab|horizontal box, change it to General.