[EventCalendar] Event category is "disabled"

[Matthias "LoCal" Schonder]

Hejsan,

I installed EventCalendar 3.1.0 but when I write a post I can not  
activate the category which is set as EventCalendar-Category. It's  
grayed out.
I have only three plug-ins acitve: EC,  EC-Widget and Sidebar-Widgets  
( V 1.0.20060711). I use WordPress 2.1

Any suggestions on this?

Thank you very much in advance.

Matthias Schonder