SureAI

Hi
I'm hoping someone here could help me, and that I'm not breaking any rules by asking this.

When I use the talent ghostwalk:
I press z and mark a target,
the target has a purple circle behind it and I get a message at the top left of my screen saying a target has been marked (in german),
but then... nothing happens.
No matter what I do, if I crouch, use my weapon, press z again, wait a while... the teleportation part just doesn't happen, and the target remains marked.

Am I using the talent wrong? Does it only work under specific conditions? Is it a bug?
Help would be much appreciated.