If Katie Couric seems a little less cheerful around CBS headquarters this morning, that's probably because America's sweetheart is turning 52 today. Others celebrating: Magazine mogul Jann Wenner is 63. Nicolas Cage is turning 45. CSI: Miami's David Caruso is 53. Kenny Loggins is 61. And Dustin Diamond, better known as Screech from Saved by the Bell, will turn 32 today.