I have worked with a few reports of this behavior reported by David Light and on the Autodesk Discussion Groups. I wanted to also include the troubleshooting process which has resolved many of these occurrences below:
Each step should be tested individually as the root cause may vary from workstation to workstation and all steps should not be required. Test rendering the same view after each step: 1. Windows Temp Folder
Close Revit 2011; then empty the contents of the Windows Temp folder at: %Temp% 2. Hotfix – Black Preview Swatch
Apply the swatch hotfix below, which contains an updated material file: Hotfix – Black Preview Swatch 3. Uninstall \ Reinstall the Revit 2011 Shared Material Library
The following technical solution outlines both uninstall and reinstall steps: Uninstalling the Autodesk Material Library 2011 If the issue persists, there are 2 additional items to verify:
Run Revit as an administrator by right-clicking on the shortcut > Run as Administrator. Verify if the results are consistent.
Log onto the same workstation with a new Windows user [preferably one that has never logged onto the workstation] and test the render with the same project \ view.