When you install an addon like SItoA, you may see an error like this the next time you start Softimage:
// ERROR : 2356 - This plug-in is not installed: ArnoldRenderPreferences
That’s because addons like SItoA install custom preferences, which are left behind when you uninstall the addon. At startup, Softimage finds the custom preference but can’t find the plugin that owns the preference (because it’s been uninstalled).
To get rid of this error, go to your Softimage user folder, and delete the Data\Preferences\Arnold Render.preset file.