Contrary to what I have thought you don't use GRUB own drivers but BIOS ones and it looks like BIOS issue. Does it happen in e.g. Windows bootloader as well?

The two keyboards (actually a keyboard and number pad) are definitely not the problem. Unplugging the keypad generally does not help. Unplugging the Wacom device has a 100% success rate. In fact, it's the only device that has any effect on this problem.

Done. There's one message printed to stderr, which you can see at line 126.

"incomplete hub descriptor, 7 bytes"

I got a new computer last April, and I found that GRUB usually (more than 90% of the time) does not respond to my USB keyboard in any way. I tried a few things to fix this, including:

- Switching between USB 2.0 and USB 3.0 ports
- Changing BIOS options (particularly toggling USB legacy support)
- Unplugging USB hubs

I eventually found that the problem was my Wacom tablet. With it plugged in, the keyboard almost never works in GRUB, but with it removed, the problem has never occurred.

The keyboard works in the BIOS, in Linux (I've run Ubuntu and Gentoo on this box so far) and in Windows, and in the Grub Legacy and Windows bootloaders, regardless of whether the Wacom tablet is present.

This leads me to believe that this is an issue specific to GRUB 2 and the tablet. I figured that I should report it, but I don't know what else I could do/mention that would be helpful.

Details:

Version: GRUB 2 rc1 (problem existed on previous GRUB 2 betas, including Ubuntu)
Motherboard: eVGA Z68 FTW (Intel Z68 chipset)
Operating systems: Gentoo (kernels from 3.3-3.5)
                   Windows 7
                   (previously, Ubuntu Precise)
Tablet: Wacom Intuos4
Keyboard: Kinesis Freestyle
          (but problem affects other keyboards)