Excel formulas not working

[jayclinton]

Ok, my boss opened his 2007 excel and he had a simple formula in. A1-1, B1-1, C1-1, D1 =sum(A1:C1). It gave him the correct answer 3. He then dragged D1 across and the answer for all was 3, but they were all adding the cells above that contained no data. So then he sent it to me. Now The sheet has the correct formulas and the correct answer of zero in the dragged cells, but if I input information for example I input A2-1, B2-1,C2-1 and already in D2 I have =sum(A2:C2). The answer is zero. I have 2003 excel. I have attached the sheet. Does anyone know how this could happen?

Thanks for the help,
Jay