I believe some of Nokia 5800 Express Music are suffering with this problem. Your screen become fuzzy when u unlocked the screen.
The solution actually is send your Nokia 5800 to the Nokia center and ask them to change your Nokia 5800 screen. I not really sure with the price they will going charge you.
However i discover it this problem will solve when your screen displaying white color. For example when you turn your nokia off, your screen will be ok.
Or when you online from your nokia and showing "white" google page, your nokia 5800 screen will be ok.
Or if you have Garmin GPS install on your nokia 5800 and you run that application your screen will be ok because the application displaying "white" display.
So i wrote this solution for those having inadequate budget for your phone screen repairing. Beside of doing all that, (which is annoyance) you can solve the problem with a little sacrifice.
You need to install White Pro Theme For 5800
Maybe some of you feel that this theme is disgusting. But this is free cost solution for your Nokia 5800. If anyone got another theme which is can be the cure of this nokia 5800 "suffered disease". You can share it here. Hope this can change your bad day with your lovely Nokia 5800.