More infos Server Admin Tool no virtual hosts

[Ute Hoffmann]

Hallo,
I think the error-page is not the problem. When I try to save  a new 
virtual host now I get:
You cannot use this function. You can file a bug if you like.

Exception:
In updateDescriptionFromConfigurationView

NSInvalidArgumentException -NSCFDictionary setObject:forKey: attempt to 
insert nil value.

Any idea what could trigger this exception in the server-admin tool for 
Apache?

Thanks,

Ute