If you experienced an update issue last night upgrading from 4.2a SR-4 to 4.2a SR-5 and are in a non-working state, here are some steps to take which should get you up and running again.
Download 4.2a SR-5 from: http://downloads.logos.com/LBS4/LBS4MacInstaller/4.21.5.0959/Logos4Mac.dmg
Copy the application bundle to your applications folder.
Open Finder -> Select "Go" from the menu bar -> Select "Go to Folder" (Shift + Command + G) -> Enter in "~/.mono"
Delete or Move to trash the "registry" folder.
Open Logos 4 Mac, and everything should start working again.
If this does not fix the issue for you, please post your logs here and we will do our best to help you out. Sorry for your troubles.