Hi.

Try to determine possible resolutions by typing "hwinfo --framebuffer". Use the
hex code 0x... and put it as kernel parameter in your grub.conf.

For 1400x1050 with kernel 2.6.24-r3 I am using the following lines:

title Gentoo GNU/Linux (gentoo-sources-2.6.24-r3)
root (hd0,1)
kernel /gentoo-sources-2.6.24-r3 root=/dev/sda5 vga=0x344


Regards,

acm.