[Project_owners] Toolbox icon?

[Gerald Vogt]

For my extension moji I have my own toolbar icon. It used to work just 
fine. Now it is only O.K. when it is on the toolbar but when it is not 
and you open the customize toolbar window it looks like in the 
screenshot here:

http://bugzilla.mozdev.org/attachment.cgi?id=4018

I have compare all settings with DOM inspector but it seems to me as if 
I do nothing different then other sidebar icons like the history button...

What am I missing here??

Gerald