If I click on Edit Motion Layer for an character with spring effects I get the message "This object contains spring effects. You can disable the spring effects by adding an OFF key in the spring track before using the Edit Motion Layer tool". This happens even if the sprig effects are turned off.

If the character does not have spring effects the link button gets toggled on and off and the edit motion layer window does not appear.

I've tried restarting the program and tried different iClone characters such as Natalie CC, Christian CC, Heidi and Mr. Pose.

Update:
I'm able to use the Edit Motion Layer after I changed the Icon and Font Size from large to medium. I double checked and changed back to large fonts and the window would not appear. So it's definitely related to the size.