Problems to select the nextcellent gallery

Hi there,

I do not know for what reason the posibility to select what galery to insert into the post from Basics -> Select a Gallery is not working anymore on my site. There are only a message ?Select or search for a gallery” displayed but no galery is available to select. To insert a galery in post i must put the tags manualy [nggallery id=****] and galery are displayed into that post. Can anyone point me what’s wrong? Thank you!