Are you running one of our products IRender nXt or ArielVision?
What choices do you see when you right click on a face which has the material that you want to edit?
I'm running IRender nXt for Sketchup, v4.0 K102nxt. Screen shot 1 shows the options when I click on the glass material. Screen shot 2 shows the Material Editor. Within that I don't see the "turn off reflections" option. Screen shot 3 shows the Transparency tab.
Try this, to get absolutely no relection:
On the main Edit Material tab, set Reflection Intensity to 0.00. On the Trans tab, set both Transparency and Refraction to 1.00 (Refraction can make the surface appear to be reflective.) You can use less transparency if you'd like, but leave the refraction set to 1.00. And on the Options Render tab, make sure that "Use Auto Reflection" is not checked, if it is available in the version that you are running (That option adds some reflection to all transparent surfaces.)
You can then play with adding back refraction, etc. to get the look that you want.