When moving or renaming files in Visual Studio .NET v2003 that are under source code control with Visual SourceSafe, here is the procedure:

1) Make sure all affected files are checked in
2) Move/rename the files using the Visual SourceSafe explorer
3) Move/rename the files using the Visual Studio solution window

The moved/renamed files should show a lock symbol indicating that the files were 'found' in the VSS database.

If the files are DataSets, the namespace will not be updated. To fix this:
1) Check out the DataSet
2) Run the Custom Tool (right click file in Solution Explorer)

For other files, just change the code manually.