Dell Latitude E7440 - HDMI and Display Port stoped working

Hi,

I have a Dell Latitude E7440, Windows 7

The HDMI-port has been working fine for two years attaching to varius units - projectors, TV etc.
Last year it stopped to work with one projector (where it uasually works) so I just used the docking station and an VGA cable instead - did not have time to look for what went wrong. After that, a few months later, the next device stopped to acknowlagde the HDMI signal, now it was my standard Samsung LED-TV. OK, so I guessed that the HDMI-cabel was the problem, but after testing several HDMI cables with no luck, I rather thought that the problem was a physical problemen in the HDMI port at the back of the laptop. To shame, hard to fix that. I now realized that there actually where another digital port on back sida of the laptop, the mini displayport -maybe that one is working? So I bought a converter "mini display port to HDMI" - and whooho - it worked. But just for a few days.. :-(

Now I am back to use the docking station and VGA and as you can understand - that is really anoying.
I have been using laptops for + 20 years now so I do think I have some experience. It is not an "Fn + F8" problem or a cable problem. Any suggestions?

/carl