I've been using 2.6.11 with Splashy, passing "vga=791" with GRUB. I upgraded to 2.6.13, and now if I pass "vga=791", it boots blind, so to speak: nothing is displayed on the screen at all, but from watching hard disk activity I can tell it's booting.
I found this thread: http://groups.google.com/group/fa.linux.kernel/browse_thread/thread/c56d269e6e2640d5/b3eb81312b468d39?lnk=st&q=2.6.13+vga%3D791&rnum=2&hl=en#b3eb81312b468d39 I'm far from an expert on something like this. Do I understand this to mean that 2.6.13 doesn't support passing VESA modes with "vga="?