[Richard Walters]

Same problem here with Matrox compressHD ver 4 I literally had to remove all instances of Compressor, the App, the Preferences the Compressor folder in Applications Support then reboot and reinstall to get it to work. Runs fine now, but Matrox says they are working on a version 4.1 for Mavericks but their Mountain Lion version is incompatible with OS 10.9