Many factors involved. The main one for me were the many crossed transmissions due to the saturated sector and frequency. It certainly didn't help matters. Furthermore, Lufthansa not having a pertinent way point in their FMS also didn't help any. I don't know what the ATC staff compliment were and how many sectors they had open at the time, so it's difficult to judge. In my mind the sector and the controller were overloaded for a period of time.