The subject line is a pretty good summary of the problem.

On occasion, I find that I cannot use my keyboard to change grub menu selections---or to modify one to, say, boot to single user.

The motherboard is an older MSI (Z87-G41 PC Mate / MS-7850) and the keyboard is the venerable IBM Model M.

The problem is intermittent and, as Murphy would have it, only seems to crop up when I really need to get into the grub configuration at system startup. Power cycling the system seems to fix it -- usually -- but I'm not crazy about doing that on a regular basis for fear of blowing a power suppply (which, in my experience, only happens when you jolt them with AC power). After the default grub selection boots, there are no problems with the keyboard either at the console level or when Xorg is running. Frankly, I think if a Model M ever truly bit the dust, it'd be on the news.

Anyone else see their keyboard or grub do something like this on their system?

TIA...

While old IBM keyboards had few equals (Northgate being a significant exception), their cables were not always so durable.

[written from a B85-G41 PC Mate with PS/2 attached keyboard]