MacPro freezes owing to Security & Privacy control panel, plays unsavory clicking music. I have to re-boot my Map Pro several times daily. It is running 10.9.4 (Mavericks, which has wrecked no fewer than four Intel machines in under two years; I would go for YEARS on a single (Power)Mac publishing magazines and editing books. Now I have three (Intel) Macs (with at least one at all times in the repair shop; SquareTrade has paid me a few grand to refund its fees as well as to pay for Macs purchased via eBay) and it appears that the problem has to do with the start-up utility in Security & Privacy. Every time I boot, I get a blank dialogue window showing the Sec & Privacy icon. If I don't immediately cancel, the machine just cycles with its spinning beachball. If I cancel the blank dialogue window (which I wish I could submit a screenshot), the machine runs for a couple of hours before it inevitably starts up its swan song of hard drive clicking—no matter whether I am running a Web browser, InDesign, Word or even nothing. The only resolution is a hard re-boot. Has anyone any solid advice as to why the Sec & privacy (as well as other such password-demanding dialogue boxes, none of which I use regularly) come up with no text? And why Mavericks seems so unstable with respect to all this? Thanks.