The halt command never works with ubuntu and its derivatives. While I was using ubuntu and typed sudo halt, it would freeze over the halt framebuffer. I could only shut it down by hard reset when that happened. But in any other distro I have tried, halt works as intended...

getting halt to (maybe) work
 

That's weird. It works with Mint, which uses an ubuntu base underneath. You might have to open a terminal as root, run dolphin as root, go to /bin, find halt, right click on it & give all users permission to use it. I would also make sure the executable box is checked.

I just used to do sudo halt, and it didn` t work (anyway, I don` t mind, as I am not using ubuntu anymore...)

I have only rarely had problems with shutdown in the 'buntus...

But as to the OP, I'm certain this is a hardware issue.

I have neither had problems. Just halt doesnt work...

run what??
 

I run that all the time when nuking a computer for a clean install.

Ubuntu and Mint are weird. They even disable root. You can't just do

su

Root password

You have to do "sudo su" instead without the quotes.

& halt still doesn't work. ???

I wonder what was going through their mind. M$ Vista disables the administrator account in a similar fashion.