I have a couple of Dell Inspiron 1525 laptops.
When typing, the cursor jumps unexpectedly to somewhere else on the page, so the subsequent typing enters characters in the wrong places.
It seems to happen most when I hit the "T-button", especially upper case T.
Do you happen to have the touchpad on? I've used those laptops before and have accidentally touched the touch pad when typing. It may seem like a silly idea - but i've come across quite a few people with that problem and the resolution was always the same.