When do and don't formulas carry down when inserting a row?

It seems to me that in prior versions of Excel,when you would insert a row, that the formulas from the rows above and below the insert would automatically carry into the insert row. In Excel 2007, it appears that sometimes they do and sometimes they don't. I can't find any consistency to this that would point me in a direction of "enabling" this feature. I am tired of having to go back and double check to make sure the formulas carry into the inserted rows. Thanks for any help.

I have a spreadsheet (HUGE of course) that totals at the bottom of several columns. I am inserting in the middle of the sheet. If I understand what you are saying, it should automatically put the formulas in the insert row. Yes? Well, I am finding that sometimes it does and sometimes it doesn't. I am looking for the key to making it do it all the time.