I just update the FAQ.
[MAC] Audio but no Video
Your computer may be trying to play the game at a screen resolution it doesn't support.
Right click on Penguins Arena application and select "Show contents", find the Contents/Resources/starter.fps/client/pref.cs file, open it with a text editor.
Change these options to the following values:
$pref::Video::windowedRes = "800 600";
$pref::Video::resolution = "800 600 32";
$pref::Video::fullScreen = "0";
Save the file and restart the game.
I hope it'll resolve your issue. If not please send me the following file :