Excel drag-fill not filling by series!

[jstn]

Here's the thing - I've never seen this before, or had this issue, and I use excel daily for the past 15 years....
When I'm attempting to use the drag-fill in excel 2010 (by selecting the bottom corner of the cell) it is ONLY copying the cell contents - I can not get it to complete the series regardless of how many cells I select initially. I can complete three cells, highlight and attempted to drag-fill, it just copies those three cells over and over, it doesn't attempt to auto fill what the next cell should be - like it ALWAYS has before

Now - I'm using a new work station, so is there something in a setting somewhere? I've tried adjusting the "fill" option to "auto-fill" but it always reverts back.....

[shg]

Attach a simple example that illustrates?