The Problem
After upgrading Blocs, the Icon Library window is blank when I open it.

The Reason
This is because the Blocs Application and the relevant Application Support directory need to reside on the same hard drive. It’s likely that your Mac has two hard drives and your Applications directory is on a different drive to your Application Support Directory.

The Solution
Make sure your Mac is set up so the Blocs Application runs from the same hard drive as the Application Support directory.

Why Did This Happen?
As of Blocs 2.4, the application uses the WebKit 2.0 WebView to drive the main design canvas. The WebKit 2.0 WebView is more modern and delivers a huge amount of performance improvements, however, it also enforces some new security features which prevent assets being loaded into the WebView if they reside on other data sources other than the one Blocs is run from.