The problem is :
/boot/grub/grub.cfg

Open file grub.cfg and find a line like this :

linux /boot/vmlinuz-2.6.38 root=UUID=1ecd35a8-0437-4c37-bb72-63d014dd846e ro text splash nomodeset vga=791

Yes it’s the problem, field vga not yet set.

Fixed:
You can replace the line with :

linux /boot/vmlinuz-2.6.38 root=UUID=1ecd35a8-0437-4c37-bb72-63d014dd846e ro text splash vga=0x791

You can do it through the console, before you type “startx” or with linux booting.

Have fun!