Excel 2007 : copied formula doesn't display correct result

Here's the problem I have multiple columns of data with a simple addition formula at the bottom. When I copy the formula from the first column where I created it, the result is the same as in the first cell. When I click on the copied formulas, the correct cells are referenced, but the result is incorrect. I don't have any "$" in the formula. If I double click on the copied formula, sometimes it becomes correct, but not always.

i.e.
A B C D
1 1 2 3
2 4 5 6
3 sum 5 5 5

Formula in B3: B1+B2
C3: C1+C2
D3: D1+D2

obviously the sum line should be 5 7 9 but it does not come up that way. In addition if I create a formula referencing the incorrect values, the wrong values are used, so it is not just an apparent mistake.

Side note, does anyone know why Microsoft has so many bugs without fixes. This is the second inexplainalbe problem I have had with 2007 and in my work could have disasterous results.

Soon to reload 2003,
Frustrated