My laptop has very annoying shortcut keys on it. I'm a very fast typist but whatever keys I hit when typing a few sentences, it sets my keyboard into doing all sorts of things like deleting what I've just written, skip between sentences and that type of thing.
Actually this happens with me also - again I assumed that it was the touchpad, but since it never happened when I was running in Vista, it may well be the short-keys. Am as interested as the OP in any potential resolution!
Try either holding down shift for a few seconds or pressing it a few times in a row, possibly 5 times - think in then may prompt about sticky keys, which may be the same thing.