I did a clean WP install (3.4.1), installed WP Super Cache (1.1) and Bulletproof Security (.47.2). Caching works normally. I then installed and activated Better WP Security (3.4.2). Caching stops. Looking at WP Super Cache list of caches files shows a cached page for a brief second then no cached pages. When I deactivate Better WP Security caching resumes. Clearly there's incompatibility between WP Super Cache and Better WP Security.