minecraft-launcher 2.1.2339 hangs trying to load / run any version of minecraft

What:   Minecraft-beta.deb version 2.1.2339 (06 Feb)

Upgraded working minecraft-launcher from 2.1.2033 (19 Dec) and launcher will no longer run any version of minecraft - it hangs at "Preparing..."

launcher_log.txt ends with:

[0207/175920:INFO:ClientHandler.cpp(1025)] Session: Wrote authDB
[0207/175920:INFO:ClientHandler.cpp(1025)] Changing view to: main.news
[0207/175924:INFO:ClientHandler.cpp(1025)] Selecting configuration Snapshots
[0207/175924:INFO:ClientHandler.cpp(1025)] Preferences: Wrote preferences
[0207/175926:INFO:ClientHandler.cpp(1025)] Preferences: Wrote preferences

Reverting to the 2.1.2033 launcher package resolves the issue - it works as expected.