I am also struggling with LX right now to get seat 2A or 2K assigned for a flight from BKK to ZRH. The answer from LX Customer Service to my request via E-mail was that they can not reserve seat 2K "without a special reason". Further I was told that 2A is already taken.
In the past I never had any problems reserving seat 2K. I never have been reseated.
Even if flying with an award ticket or an upgrade LX should not treat loyal customers like that. I fully understand that they have to add the disclaimer that you will eventually be reseated. But I do not understand that they refuse to make a reservation for seat 2K at all.
@thyeri: Please let us know if you were succesful to get seat 2K by phone.