It appears this is not due to libcairo, but binary incompatibilities with xorg 7.1. More information at http://www.nvnews.net/vbulletin/showthread.php?t=72490 - subsection entitled "Any distribution with XOrg 7.1". -- nvidia not compatible with Xorg 7.1 RENDER (Fonts don't appear in edgy) https://launchpad.net/bugs/55802