Solved: Ubuntu 10.04 (Lucid Lynx) boot up resolution

After installing the proprietary NVidia drivers for my graphic card, the boot screen resolution has changed to 640x480. It didn't look good at all the with the nice splash screens provided by plymouth. To resolve the problem I have added the following two lines to /etc/default/grub

GRUB_GFXMODE=1680x1050
GRUB_GFXPAYLOAD_LINUX=1680x1050

To activate the settings, use

sudo update-grub

Here the 1680x1050 is my screen resolution.

To select a nice splash screen, use

sudo update-alternatives --config default.plymouth

That's all