I found a solution.
I unplugged my USB "expander board". I don't know the real word, but the thing you plug into a USB port and it gives you 26 slots in return...
And... It booted perfectly...
Any idea how that could have had an impact?
It comes back to my original theory that your computer was looking for hard drives, 26 possible drives would take a long time to check as it would wait for a few seconds for the ready signal on every possible drive