I've owned two Nokia N92's and both of them seem to have this same problem: dust gets behind the screen.

The problem was so bad in the other one that I couldn't even use it, and had to sell it on eBay "as is".

I proceeded to buy a near mint condition N92 hoping for the best, but what do you know: the phone is in great condition but there are dust particles behind the screen. Keep it one day in your pocket, you got a hundred more particles.
After a week you don't even want to look at the screen anymore and you have to take it apart for cleaning.

Any ideas how to fix this? I'm not sure where the leak is, it's either the edges of the screen casing or the speaker holes. I'm thinking it's probably the speaker, or at least it would seem obvious because there are two holes right above the screen.