An update is required to detect Spring Security 3.0. A user patch has been located:

static {
        try {
            AcegiAuthenticationClass = Class.forName("org.acegisecurity.Authentication");
            AuthenticationClass = AcegiAuthenticationClass;
            Log.debug("Acegi Security detected.");
        } catch (Throwable t) {
            Log.debug("Acegi Security not detected.");
        }
        try {
            SpringAuthenticationClass = Class.forName("org.springframework.security.Authentication");
            AuthenticationClass = SpringAuthenticationClass;
            Log.debug("Spring Security detected.");
        } catch (Throwable t) {
            Log.debug("Spring Security not detected.");
        }

       // New code below

        try {
            SpringAuthenticationClass = Class.forName("org.springframework.security.core.Authentication");
            AuthenticationClass = SpringAuthenticationClass;
            Log.debug("Spring Security 3 detected.");
        } catch (Throwable t) {
            Log.debug("Spring Security 3 not detected.");
        }

       // end patch

    }