Sometimes the "Fill Series" functionality does not work as expected. On most
sheets I can type numbers 1, 2, 3 and select them and fill down with numbers
incrementing as high as I like, example 1, 2, 3, 4, 5, etc. Sometimes when I
try this it just repeats 1, 2, 3 over and over again.

There seems to be nothing unusual about the column. It is not sorted,
filtered, or formatted any special way. If I create a new sheet it will fill
down as expected. Also I find under the "Edit/Fill" menu the option for
"Series" is gray.

I dont think the problem relates to anything in the "Tools/Options section
because most sheets work as expected. The current sheet I am working on is a
copy and paste from another excel file.

I use Excel 2003 SP3

Any thoughts on why this sometimes happens and what I can do to fix it?

Quin