Calibrate your screen folks.

N900 thinks you put your pen down from inside the page. make sure you are at 1.2, otherwise install the calibration fix. If at 1.2, don't get / remove calibration fix.

Touchscreen is larger than the actual screen, that's how N900 knows you swipe from "outside". If it's miscalibrated, it doesn't know.

Additionally, some issues exist where the left side of the screen is less sensitive. Make sure you use some pressure. Use a soft point, I like wooden toothpicks, because they crumble on too much force and make sure there's pressure.

@princesaqib
a) does it work when swiping the other way? Right-to-left should get you into history
b) please, please stop waving the camera when shooting. Stable is the way to go. I'm not watching that again. If you need your hands, get someone to hold the camera or use a prop to hold it. Use some books and hold the N900 vertical.