Excel 2007

I have noticed that the horizontal Axis options can change in an Excel 2007
chart, which is driving me crazy. On some charts when I open the horizontal
axis options, under Axis options, they start out with "Interval between tick
marks", "Interval between labels" and so on, which is what I expect to see.
On another chart, with the exact same layout and data (just the numbers are
different for the data), when I right click the horizontal axis and choose
Format Axis, the Axis Options start out with Minimum, Maximum, Major Unit,
Minor Unit and so on. The options, Interval between tick marks, Interval
between labels and so on are not there. These are all simple line charts
with a date column and then 2 columns of data (numbers).

So how do I get the "normal" horizontal options back? Why is Excel changing
the Axis options?