Cursor skips lines while typing

Hi,
This is an ol Acer travelmate 290. It quite suddenly starts skipping back at random while typing text ( like now !) to re position the cursor back a few lines ( so i find myself typing in the middle of stuff i've already typed!).
Its irritating to say the least. A solution will be appreciated.
Thanks.
My specific problem is, or was, that the skipped characters back to former lines of type, inserting characters in other words, started only a few days ago, and mostly in the body of the email text in gmail. It also happened in online forms such as this one and in notepad. but it doesn't seem to be happening now. A Dell Chat agent looked at the settings on the wacom tablet and asked me to disable the scroll and put all other settings on default.I was inclined to think that while typing in gmail text in the body of the email that I was hitting some other key, but I didn't know which one. I don't think the pads of my thumbs are hitting the touchpad. so I'll see if this never happens again I'll consider it fixed by the online helper.