Could someone please translate into German the phrase "When did you last see your Father?" 

I would use babblefish but it would probably translate into something like... "How long are your Father's eyeballs?"

Wenn hast du fur die letzte Mahl deine Fater gesehen? (fur is written with umlaut)

Hi, I'm german :-)

Wann hast Du das letzte Mal Deinen Vater gesehen?

Every organisation rests upon a mountain of secrets ~ Julian Assange

If you want to address the person formally, use "Wann haben Sie Ihren Vater das letzte Mal gesehen?", otherwise Puntomaus' translation.

Hi, i am german too.... Take Puntomauses version. I would guess Eddy is from the netherlands. It is understandable, but not correct.

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

Avatar image of me done by Chidori. 

As a rule of thumb to decide between the formal and the familiar 'you': if you would address the person by first name ("John, when did you ...") use "du", if you would address the person by last name ("Mr Doe, when did you ...") use the formal "Sie".

Thanks guys. So would that make it "Wann hast sie das letzte Mal Deinen Vater gesehen?"... or have i totaly screwed the grammer?

To "John": "Wann hast Du das letzte Mal Deinen Vater gesehen?" To "Mr. Doe": "Wann haben Sie das letzte Mal Ihren Vater gesehen?" To "Mr. John Doe": "Screw it, you can't remember anyway!" ;-)

Attached Link: http://www.renderosity.com/mod/gallery/index.php?image_id=1383154

Thanks everyone, but after listening to family (can't avoid them) i've gone with the english anyway. If you want to see the pic its at the link. Be advised though, it is WW2 oriented.