Fixing VLC and Matroska .MKV files on Snow Leopard (Mac OS/X 10.6)

Taken from http://fhf.org/archives/405

The problem: when VLC starts to play files it complains

m_el[mi_level] == NULL
arrrrrrrrrrrrrg Up cannot escape itself
[ass] Init
Fontconfig error: Cannot load default config file
[ass] No usable fontconfig configuration file found, using fallback.

The solution:

sudo chmod a+w /usr/X11/var/cache/fontconfig