This week, CBS' Lenny returns from limbo. This sitcom, starring Lenny Clarke as a rough, likable, working-class guy, has been one of the few consistently enjoyable new shows this season, but its poor ratings as an 8 p.m. Wednesday show caused the network to yank it and tinker with it for a while. But like several other shows right now, the problem with Lenny is its time slot. Lenny is about a family with young children, but it's not a kids' show its savvy view of grown-up life belongs in a later time period (and probably even later than its new Saturday at 8:30 time slot). The same is true of NBC's on-hiatus Parenthood: What was this crisply complex sitcom doing on at 8 on Saturdays? Similarly, Evening Shade is the year's most sophisticated new comedy, but it was getting murdered on Fridays at...8. What did CBS do? Moved it to Mondays at 8. This is why my mother calls every Tuesday to ask if I taped Shade like lots of other fans, she's just not ready to sit down and watch TV at 8 p.m. Although Shade has shown some ratings improvement on Mondays it's even beaten The Fresh Prince of Bel-Air the show is still not reaching the huge number of adults that it could and should. Even more established shows are suffering from The 8 P.M. Mistake: Fox's Emmy-winning In Living Color hasn't yet made the ratings breakthrough it might have, in part because the grown-ups who like it forget that they have to be in front of the TV at 8 p.m. on Sundays. Come on, network programmers, these shows aren't kiddie fodder like Who's the Boss? or Full House let them reach the audience that would enjoy them most.