tunn3lratz, is your finger/stylus perhaps bouncing off the edge of a screen protector?

More likely is that you're not using enough pressure. The edge pixels on my N900 seem to be much less sensitive than the ones over the rest of the screen. If you don't use enough pressure as you go over that edge, the critical first row of pixels won't respond.

Also, are you able to swipe in from the right-hand-side to bring up the browser history? It's the same gesture, but from the opposite edge.

Regards,
Roger