Strange: Sidebar is changing preview and Store button greyed out

I’m using FM4.5.2 and Yosemite 10.10. During work on my actual project the sidebar is changing from normal view with hooks on used pictures to darkened picture names or invisible picture names. After restart of FM all is ok for a while and happens again.
Additionally I’m confused that sometimes after a lot of changes the save button is greyed out. My workaround is copying all from actual storyboard and pasting it in a new project.