Preview Bit Depth Option

Press the [Preferences] button on the Main Dialog to see this option.

The checkbox in the Preview Bit Depth section of the Preferences Dialog allows you to enable or disable the use of 30 bit color. 30 bit color on systems with a GPU and monitor that are capable of rendering at 10 bits per color channel (red, green, blue) can give you smoother gradients.

Try disabling this setting if you do not have a GPU/monitor advertised to display billions of colors and/or your system is displaying corrupted data in the preview display.