If you have imported a model via the Model Chooser and find that After Effects now crashes any time you open the Chooser window, try resetting the Chooser's cache file.
To do this, delete the following file:
~/Library/Application Support/Red Giant/Trapcode/UserAssetManifest.rgam
This file typically needs to be removed and reset if Trapcode had an issue with a specific model that had been imported into its browser. Since there are innumerable configurations of geometry, animation, and encoding that can make up a 3D model, there are invariably some elusive combinations that the plugin just hadn't considered.
If you encounter this issue and the steps above failed to help, please contact support and-- if possible-- share any problem model files so the Trapcode team may continue to learn where improvements are available.