Kappy has the answer.
Its usually a duplicate font issue. Since Courier Final Draft is not the standard Courier that is installed by OS X I would suggest you remove the font.
Apple – Support – Discussions – Help not working …. Drosser points out the solution.
TidBITS Safe Computing: Apple’s Security Past Defines Its Future. Concerning isn’t it? The article states:
Just yesterday I saw engineers at security software maker Immunity (in a Web-based demonstration) exploit an up-to-date version of Mac OS X 10.6 Snow Leopard via Safari using a new, unpatched, WebKit vulnerability. All it took was a clicking on a single link to give the attacker full control over the Mac.