I hope this might be useful for others: I was having trouble opening templates in Protocase Designer for Linux until, looking through the debug.0.log file, I noticed this line:
When I took a look at my actual installation, I discovered that the install script had created the directory name with a space between the words "Protocase" and "Designer":main library missing: /usr/local/share/ProtocaseDesigner/library
Changing the directory name solved the problem./usr/local/share/Protocase Designer/library