Fill handle not increment a sequence

Jluisnun 

I had the same problem and none of the responses worked; and, like you, it was working great and then suddenly stopped incrementing.  But then I noticed when I inadvertently clicked on a cell I was copying (using CTRL D to copy the above cell) that I had accidentally put in a blank line using ALT>ENTER (enters a return to a new line in a cell).  I deleted the line with a backspace and VOILA, the drop and drag with increment began working again.  Since I was copying all my cells using the CTRL D function, I was copying that blank line each time and I can only assume that the drop and drag feature just did not see the number above the blank line as anything but text.  Anyway...another problem solved in my world!  Hope this helps in yours!