I feel as if someone is playing a cruel joke on me...please help.

I have a row of cells that show dates.

The format is set to date - nothing custom or unusual about it. Anytime I
place the date 6/30/2008 into this row excel displays "1/0/1900". I tried to
recreate the problem on other tabs of the workbook, or in new workbooks and I
can't.

What in the world is going on here?