Some when I installed the Blocs v51.0b4 it became my default. ;-( Unknown to me when I opened a project and after spending an hour working on it Blocs crashed. I allow it to re-open. Then all of a sudden the project page I was working was white. Nothing was on it. I tried to close the project. After waiting 10 minutes, I released Blocs was locked. I tried to closed Blocs. Needless to say I had to force close the App. I cleared my OSX cache. I tried to open Blocs v5.08r same. Same scenario.
It is a good thing I have a backup. I opened the project in Blocs 5.08 release and there everything was again.