USB1 module. I also had to take settings from /etc/modules.conf to /etc/modprobe.conf This was especially annoying since I use a USB
There is a script with the 2.5 module tools to generate a conf file from your existing one. It knows some of the name changes but submit others to Rusty Russell
like PS/2 support. Loading USB modules in rc.sysinit a very poor substitute. Grub also needs native USB support. Currently it only works with USB legacy support turned on in the bios.
Grub has size constraints like all boot loaders. USB is non trivial. I agree in the longer term that Grub would benefit from native USB keyboard although EFI firmware may one day make that problem go away (or become different or something like that 8))