This could be helpful.
On Friday, Apple released X11 Update 2.6.5, the most recent version of its X11 system for Mac OS X. The new version, a 7.5 megabyte download, resolves an issue that may cause X11 applications to unexpectedly quit under Mac OS X 10.7.5.
The X11 Update 2.6.5 requires an Intel-based Mac and Mac OS X 10.7.5 or later to install and run.
If you’ve tried the update and have any feedback to offer, let us know in the comments.