I have: Win7 Home Premium (since October '09), 64bit Dell Inspiron 518, ASUS 24" monitor. I use Avast! "protection" For about 4 days, I've not been able to invoke any screensaver, display OFF or SLEEP. I've changed all settings for these actions and changed back. I've started up (with) Clean Boot twice. I've made sure all my drivers are updated...they are. I've uninstalled any/all 3rd party screensavers. Nothing has changed.