Okay, this one gets me interested.
First of all, have you tried logging in (on the laptop) in the house, does it add the extra character then?
Secondly, if it does not, do you let your laptop remember passwords, or do you chose to type it in every time?
Lastly, I have on occasion had a similar issue because of the way I store and use passwords, the extra character is a space after the last letter/number, have you tried something as simple as deleting the final character before hitting enter?