I'm not sure whether this is a feature but it's very irritating. When you double click on a border of a selected cell, you go to the end of the list depending on which side of the selected cell you double clicked on. How do you disable this?
The feature can be turned off, fortunately.
In Excel 2013, (for Excel 2010, which you have, see below) File > Options > Advanced > uncheck "Enable fill handle and cell drag-and-drop". If you don't need to use those features and are OK with unchecking that checkbox, then this solution will work for you.
In Excel 2010,
"1. Go to File > Options > Advanced > Enable file handle and cell drag-and-drop 2. Check this box. 3. Click OK and you’re done" (source: http://reviewofweb.com/how-to/enable-cell-drag-and-drop-excel-2010/)
I tested this solution in Excel 2013 and it works immediately after unchecking the box and saving. The change that you see is that with the checkbox checked, and with a cell selected, the "plus sign" cursor converts to a four-arrow cursor (arrows that have ends in center and each point along axis -- i.e. up, down, left, and right). With the checkbox off, that arrow cursor never appears. Also, of course, if you double-click the selected cell edge, you are not navigated to the bottom of your section, automatically.
Source for looking at this checkbox in the first place: rhapsodie's comment in: http://ask.metafilter.com/55958/Excel-mindless-list-jumping
Mikes answer works but unfortunately you you lose both the irritating double click feature but also your drag and fill.
Alternative solution - Get out of the habit of double clicking a cell. If you just left click a cell and start typing on your keyboard you should be able to just go ahead and edit the cell.
I am used to double clicking (don't know why) but simple left click works.
Edit: A single left click on a cell followed by typing will overwrite the cell's contents. F2 will allow you to edit in the cell. Alternatively, double left click followed by typing will insert what you typed at the cursor location when you did the double click.