I am entering

12/31/06
Enter

in a cell and the spreadsheet is inserting and ='s sign before the 12 and
performing the calculation 12 divided by 31 divided by 6. The only way to
get the date to display has been to enter an apostaphe before the 12.

This only happens in this particular spreadsheet. I have looked through the
Options but I don't see anything obvious - does anyone know how to fix this?

Many Thanks,