I was able to get my PS/2 mouse and keyboard working again, at least once, by simply reloading the psmouse module remotely.
Code:
sudo rmmod psmouse
sudo modprobe psmouse
I found this out just some 10 minutes ago, so I'm not sure if it will work again next time.
I haven't found any error messages in any logs, but suddenly the mouse and keyboard just stop working.