It appears (to me) that there is a error/ommission in the net beans instalation on the Mac OS X.

The directory .netbeans and .netbeans-registration are created with the owner of root.

Simple fix 

sudo chown $USER ~/.netbeans
sudo chown $USER ~/.netbeans-registration

mkdir .netbeans/6.8
mkdir .netbeans/6.8/config
mkdir .netbeans/6.8/var
mkdir .netbeans/6.8/var/log
mkdir .netbeans/6.8/var/cache
mkdir .netbeans/6.8/var/cache/lastModified
I am not sure it all or any of the mkdir are needed but it worked for me.

The key to finding this was executing from the command line: 

 sh /Applications/NetBeans/NetBeans\ 6.8.app/Contents/Resources/NetBeans/bin/netbeans
as suggested by Yulia Novozhilova.

You might also note that the README.html file is in the /Applications/netbeans/NetBeans 6.7.1.app/Contents/Resources/NetBeans directory. Hope this helps someone.

St Als