CBS' latest statement on David Letterman's health: The network doesn't have any idea when he'll be back. Bouts of shingles can reportedly last three to five weeks, and Letterman is currently in week five of his absence from ''Late Show.'' That rivals in length his only other sick leave in 21 years, for heart surgery in 2000. (NBC counterpart Jay Leno has never taken a sick day in his 11 years on ''The Tonight Show.'')
Filling in for the eye infection-afflicted host this week: Paul Shaffer filled in for his boss on Monday, Bill Cosby is scheduled for Tuesday, and Luke Wilson on Wednesday, followed by scheduled reruns on Thursday and Friday. Wilson is the third star of the movie ''Old School'' to guest-host for Dave, after Will Ferrell and Vince Vaughn. Dave had better recover soon, or we'll be seeing Artie Lange, Elisha Cuthbert, and Seann William Scott at his desk.