>>First of all calling glGetString(GL_EXTENSIONS) does not return wglGetExtensionsStringARB!!
glGetString should return a list of extensions, not a functions.
may by you didn’t init GL extensions(GL and WGL/GLX -use glew.sf.net in this case)?
WGL_ARB_buffer_region is a WGL extension, not a GL extension. Use wglGetExtensionsStringARB instead. If the extension is supported, use wglGetProcAddress to get pointers to the functions added by the extension.
One other note, do not name the function pointers the same thing as the functions. So, don’t do: