Comment 7 for bug 129725

I have found a fix to the problem in my case.

So it seems that in my case (see post #6), the keyboard and touchpad are connected with ps/2 on a i8042 controller, who is not that well supported by the kernels for quite a while (based on info I picked up during my research, this problem exists for quite a while).

The fix that works for me, is to pass the arguments i8042.direct and i8042.dumbkbd to the kernel via grub. But these arguments are for me... for other laptops, maybe other arguments would do the trick. Here's a link I found with a good enough sample of options concerning i8042:
http://lightrush.ndoytchev.com/random-1/i8042quirkoptions

So maybe others could check this fix and post back... Then we can have a good idea if this is the common source of the problem... Here's how:

First check if the laptop is actually using that controller, by running
dmesg | grep i8042

that would give you an idea. So if the controller is there, there is a chance that fix might be for you. Then check which kernel you're using running
uname -a

Then go to /boot/grub/grub.cfg and find which entry calls the kernel that's used. Go to the line that starts with 'linux...' and then has the name of the kernel. Then, go at the end of the line, and add the i8042 options that you're trying. Example,
i8042.direct i8042.dumbkbd

Cheers