This bug is fixed since HxMusicConverter 1.3.1. Please download the latest version.
In some Power PC Mac, after you installed the app (1.3.0 and lower), your system will crash. If you have this problem, start your mac to target mode, find the file /System/Library/Extensions/HxVirtualCD.kext and delete it. Restart and you'll be fine again.
At version 1.3.1, the virtual cd kext move to StartupItems and loaded after system startup.