Apple published the following link about a potential issue with certificates when using 802.1x on Mac OS X systems with EAP types that utilize server-side certificates (PEAP, EAP-TLS, etc). The doc describes the issue and provides a workaround.
http://support.apple.com/en-au/HT203841
The issue would most likely manifest symptomatically where other wireless clients successfully authenticate and roam, but Mac OS X clients uniquely would not.
