(http://img38.imageshack.us/img38/576/freedomofmovement.jpg)
While this probably isn't a bug as much as a mistake on the information page: the spell Freedom of Movement only gives immunity to Flesh to Stone, and not petrification as a whole. Perhaps this could be updated on the website and on other sources?
Explaination: A Basilisks Petrification gaze was unaffected by the freedom of movement spell entirely, causing the protected individual to be turned to stone.