I just installed Ubuntu 12.04 on my MacBook air I had a small graphic problem described here: Recent LCD trouble with 12.04 on 2010 Macbook Air 11 (3,1). So I followed the answer and installed the latest Nvidia driver, but now my air won't suspend when closing lid, but it does work if I suspend manually.
I read in the link ( https://sites.google.com/site/easylinuxtipsproject/bugs#TOC-Hibernate-and-suspend-don-t-always-work-well:-they-make-some-computers-malfunction-or-even-enter-a-coma ) that it's a known issue. The author of the page reckons that "Suspend" be turned off. I am not sure whether a fix is available for this known issue.