The app settings should match your monitor settings.  In this case, your work monitor with Gc=2.4 will project a darker image.  However, newer monitors are shipping with higher Gc values these days.  You should untick the Gc=1.8 in the Carrara app and go with your native settings.  It appears that Carrara was set to match MAC monitor settings rather than PC.  If you are using PoserPro or using Gc shaders within Poser 7, set Gc according to your monitor output.