I've got a new screen and everything is ok now. I'm wondering now why the problem wasnt showed when using some apps like backupmenu for exemple. The xterminal also suffer only minor cosmetic problem and i was still able to use it. Does It could be a resolution screen related problem? Anyone knows how can i change (get down) the n900's screen resolution ?

Just an update:
Firstly, when i said at the previous post that i got a new screen, i was meaning that i did change all the screen (not only LCD), touchscreen and that metal slider included. I did it because i got a used N900 and just for save work, i just took off all that thing and got my device easy way fixed. But after that, i did order a new LCD that will supposelly fix the other N900. Sadlly, when the new screen arrived, i found out that the issue wasn't the LCD because the problem still there after ressembling with the new LCD one. So, now i just ordered a new flex ribbon. As soon as i got it tested i'll report back.
I hope someone could barelly understand this s* of english. Still learning.
Thanks all.