A Fujitsu KB910 USB keyboard connected to a Dell XPS 8300 used to work flawlessly. But it then started to be unresponsive now and then on BIOS level, i.e. it was no longer possible to enter the user password into the BIOS entry screen. Pressing the power button of the PC was the only way to get it working, and it worked in 100% of all retry cases.
What could be the reason?
I have tried to use other USB ports, reset the BIOS, etc. The keyboard gets power via USB as indicated by the Num-Lock LED. The outages occured in about 10% of all starts.
The problem also occured with a Cherry keyboard. Therefore, it seems to be the Dell XPS 8300. I removed all USB-related entries from the BIOS list of boot devices. But this does not seem to help.