Troubleshooting the OS X installer

Problem: nrngui and neurondemo fail, and the error message says something about
dyld: Library not loaded: /opt/X11/lib/libX11.6.dylib
Solution: X11 is missing. Previous versions of OS X would install X11 automatically, but now you have to install xquartz from http://xquartz.macosforge.org/
Problem: No gui when NEURONDEMO is launched.
Solution: This happens when you try to use the X11 version of NEURON but X11 hasn't been installed on your Mac. The fix is to install X11. If you have OS X 10.3 or later, the X11 installer may already be on your hard drive, or on one of the system CDs. Otherwise, you can go to the independent XDarwin site (http://www.xdarwin.org/) and install from there.
Problem: Can't compile mod files.
Lion and Mountain Lion both need the latest version of the command line developer tools to compile mod files. Go to http://developer.apple.com/opensource and click on the "Download command line developer tools . . . " link. You'll have to sign in with your Apple ID and password.
Problem: I want to use parallel hardware to handle large models or speed up simulations.
Make sure that OpenMPI has been installed. Download this file
http://www.open-mpi.org/software/ompi/v1.6/downloads/openmpi-1.6.tar.gz
Then
tar xzf openmpi-1.6.tar.gz
cd openmpi-1.6
./configure
make
make install
You shouldn't have to do anything special to environment variables--all these things are supposed to find each other automatically.
Problem: mknrndll does not work.
Solution: Install the Development environment that came with your system. The installer may be on your hard drive or on a separate system CD. Check the current OS X page to see if Apple mentions whether using the installer's default choices actually installs enough of the development environment. It is the "XCode" package that you need to install.

If you can't find your system CD, you can download XCode from the Apple web site. Be sure to get the version of XCode that matches your OS version, e.g. 10.4, and processor, e.g. Intel.

Problem: How to get "focus follows mouse" behavior, so you can move to a window and press a button with just one click.
Solution:
   defaults write com.apple.x11 wm_ffm -bool true
Jonathan Simon tells me that a related option
   defaults write com.apple.x11 wm_click_through -bool true
disables the default behavior of swallowing window-activating mouse events.