My samsung sgh e490 has
The reason your phones has a constant white display is simply because there is a problem with the flex of the phone.
If the screen is not damaged in any way, then the assumption of it being the screen is absolutely correct.
To fix the flex of the phone;
1. Get the appropriate screwdriver,
2. remove the battery, the battery cover, and your sim,
3. Turn the back of the phone,
4. you will see five rubbers,
5. pick them off with a pincher,you will see screws under them, unscrew the phone,
6. Get a credit card and slip it through the line around the phone then apply a little force in separating them apart,
7. you will see the panel of the phone, carefully lift it up,
8. you will see a flex that runs through the screen to the panel, carefully detach the flex from the panel,
9. unscrew the screen of the phone, remove the flex connected to the screen also and replace it.
10. Reverse the process to reassemble the phone.
And also it might be a damage LCD (glass screen) ,
defective display driver (small chips that makes the display works)
and the other one is corrupted software...in damage LCD the phone will detected
on Feb 19, 2011