From Jean-Sebastien Guay, "After a bit more testing, it was still not 100% robust, so this fix

will bring the change in line with what is done on other OSes (Linux)
and works in all tested cases.

For reference, this was tested with:

osgviewer <file>.wrl                (file in current directory)
osgviewer <dir>\<file>.wrl          (file in child directory, relative)
osgviewer .\<dir>\<file>.wrl        (file in child directory, specify current)
osgviewer <drive>:\<dir>\<file>.wrl (absolute path)
"

src/osgPlugins/vrml/ReaderWriterVRML2.cpp

@@ -81,13 +81,13 @@ osgDB::ReaderWriter::ReadResult ReaderWriterVRML2::readNode(const std::string &f
     std::string unixFileName = osgDB::convertFileNameToUnixStyle(fileName);
 
 #ifdef WIN32
-    fileName = "file://" + unixFileName;
+    if(unixFileName[1] == ':') // absolute path
 #else
     if(unixFileName[0] == '/') // absolute path
+#endif
         fileName = "file://" + unixFileName;
     else // relative path
         fileName = unixFileName;
-#endif
 
     std::fstream null;
     openvrml::browser *browser = new openvrml::browser(null, null);