Give this a try
First make a backup of your original sys
Then delete this from sys file

[rawdisplay]
driver="gdi"

resolution_dir="800_480"
vga=1

[rawdisplay]
highres=0
screen_x=800
screen_y=480


Replace with this

[rawdisplay]
driver=engine
screen_xy="auto"

Delete folder SAVE (in same dir where the sys file is located)
Reboot device and try again