I used the glass material wizard -high grade.
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Steps:
-Open fresh copy of max (2011).
-Make a maxwell glass material using wizard
Render preview
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I think the problem may be that rs0, the engine used to render in FIRE, is being used for both the production AND the Draft material render in 3dsmax. Rendering a glass plane on a white floor in a default maxwell scene with FIRE shows it just as dark as the rs0 engine's material preview of it.
Rendering it for real shows it as crystal clear glass.
--edit-- It's worth nothing that the FIRE version shows it as dark as well. Glass used to work fine though in the previous version of FIRE.