Warning BHT0004: Multiple matching projects were found. Only the first one found will be built.
The BuildHelp build task found more than one copy of the project file in the MSBuild global project collection.
This error is unlikely to occur as MSBuild.exe does not currently appear to use the global project collection when invoked from the command line. If you encounter this error, please open a work item in the Sandcastle Help File Builder project at CodePlex containing the details of the build and attach a small example project with any related files that can be used to duplicate the problem.