Customization of related lists fails

Customization of related lists fails

HI there,
I've got a problem with customization of my related lists (e.g. contacts, leads). I followed the instructions given in the help files but to no avail. Whenever I added a new field, clicked save, and went back to the list, the order and number of fields remainded unchanged. I am administrator. 
So what went wrong?
Thanks for any help
kind regards
Armin