This is a known issue. To correct the problem, replace the RegisteredTools, Tool Catalogs and ToolPalette subdirectories from a computer where the subassemblies are working.
If you don't have access to a computer where the subassemblies are working properly, follow these instructions.
1. Copy the entire
2. Modify the deployment and proceed through the configuration steps to update your deployment.
3. Repair your installation of Civil 3D 2010, using Add or Remove Programs in the Control Panel (Windows). Select the Reinstall option.
4. Start Civil 3D 2010 and confirm that tool palettes have subassemblies.