date formula not working

cell B1 contains the date "7/1/12"
cell D1 contains the formula =B1+1 and it correctly displays, "7/2/12".

When I copy that formula in to cells F1, H1, etc., it does not carry the math out even though the relative references appear correct.

I have several identical spreadsheets and this is the only one with a problem and I just cant figure it out. I will attach the affected spreadsheet for reference.