Hello,
Well i had some time and looked up if i had XMP enabled, but unfortunately I haven't.
In the meanwhile have I also tried the memory in an anther pc here at home, which gave 1 working and the other one not working so i guess it will be a faulty memory chip then.
will be sending them back to the store and wishing better luck with the other new ones.
thanks for the replay, at least i learned a bit more about the XMP.