IF the car starts after unplugging the fuse...It points to the relay Behind the glove Compartment. The relay is a Green one (about $15) .. The relay sticks sometimes which is why the problem is intermitment.

You know what,it makes sense and I am gonna go this way,and remove the relay and check that out.
You say it's green,is it the only green relay over there?

There is only 1 Green one there. For the cost of the relay . I would change it and then see if the problem goes away . You can try and switch the relay with the Rear Heating one from the Right boot area ( it is the same relay and easily accessable

Sounds good,will post once accomplished

How is the green relay accessed? Do I need to remove the glove box, or is ir accessible with the glove box in place?

PS, mine's a UK car if that makes a difference.

You have to remove the Glove Box and then remove the screws holding the the fuse rack in place There are 4 or five screws. The relay is behind the fuses and can only be seen after you move the rack. There is a picture on the board here somewhere... do a search...

I just tried to alternate the relays and got the same result.
So,there's a tendency when I turn the key into position #2 I hear "clink" 1 second pause "click" in this case the X starts with no problems,but if I don't hear any "click" before I start to crank,no start.
So,now I disconnected the Negative and taking the tea break I am gonna check out if the same tendency continues after the "brain wash" :)
If it does,the only thing I may think of is the Ignition Switch.
Fuel pump works fine I assume,since the pressure is up in less than a second.
What do you think?

My 2005 4.8 does the same. I can get it to work every time when it acts up if I hold the gas pedal all the way down, then let it crank for about 20 seconds, then it starts. No idea how to fix this though.

I find with mine that, when it's not starting, it will still sometimes catch and start for a split second, but die instantly. I'm guessing it can't be the filter as that wouldn't be intermittent wouldn't it?

Today it's been perfect. We're trying the spare key to see if it's the immobiliser.

Bloody annoying!!!

Had the same thing once in a while.No help switching the keys anymore..so it's not an immobilizer.