When viewing the ArcToolbox in ArcCatalog or ArcMap, only the top level of toolboxes, such as Cartography, Data Management, and Conversion tools are visible.
The ArcToolbox Template has become corrupt.
Solution or Workaround
Find and rename the Arctoolbox.dat file.
- Navigate to C:\Documents and Settings\<login>\Application Data\ESRI\ArcToolbox
- Rename arctoolbox.dat to arctoolbox_old.dat
- Close all ArcGIS applications and then open ArcCatalog again.
The tools should now be visible.