I recently experienced a "Hard" Windows 7 Professional failure where the OS notified me it was closing down to protect components. In the process it apparently corrupted certain files essential to Logos 4 and Windows ability to work with it.
My Logos would only show the perimeter of the "Layout" I was using when opening Logos. The probelm was resolved by my techie son. He discovered that font files had been corrupted during this shutdown process which prevented Logos from finishing upon startup.
I went 8 days and through 3 Level 2 techs and finally the head of development (I was told this person was head of development) and did not get any farther than it was a problem with Windows and the WPF. I was instructed to fix the corrupted part(s) or reinstall Windows. You all know what that would have meant. I already removed Logos and reinstalled it which including indexing took 3 days.
So look out for corrupted font files that prevent Logos from executing.