Tafflyer, thank you so much for bringing my attention to your issue from last week. I'm sorry you also had to deal with this. It is aggravating, as it's essentially false advertising when the websites quote a price and won't allow it to be carried out. I appreciate your chiming in, as it's saving me from virtually banging my head against the LH website wall multiple times.
I just called LH's Internet Service Center, and ended up being quoted around +95 EUR from my first attempt on Saturday morning. I chose an earlier first-leg flight, and after some wrangling, got the phone service charge removed, which brought it down to +25 EUR. Unfortunately, phone service wouldn't allow me to apply my freq flyer points to further lower the price. Grrr...