From LightWiki

You press the F9 or F10 key to render your image or scene, and somewhere during the rendering process the render panel says its rendering transparent items. The problem is, you didn't have any, and these transparent items are adding time to your rendering!

There are a few reasons why this may be happening.

Fast Fresnel shaders - Check to see if any surfaces have the Fast Fresnel shader included, then check that there are no Transparency options active in the shaders properties.

Other Shaders - Also check for any other shaders you may be using, including 3rd party ones you have downloaded from the internet. Check them to see if they change the transparency of a surface in any way. If unsure, untick the shader in the list and render to see if the transparent items message goes away.

"Unaffected by surface" in Alpha - Under the Advanced tab of the Surface Editor, check to see if the alpha channel option 'Unaffected by surface' is set. For LightWave to achieve this effect in the alpha channel, surfaces are marked as transparent so that they do not block the geometry behind them.

Additive Transparency - Under the Advanced tab of the Surface Editor, check to see if any surfaces have an additive transparency greater than 0%. This will make surfaces transparent even if the Transparency for that surface is set to 0% on the Basic Settings tab.