NBC has given a full-season pickup to the freshman TriStar TV comedy “Mad About You,” starring Paul Reiser and Helen Hunt, bringing its total order to 22 episodes.The series has done what NBC wanted in its Wednesday time period, holding on to an average 96% of its “Seinfeld” lead-in rating. Unfortunately for NBC, the “Seinfeld” numbers are lower than anticipated due to ABC’s scheduling of “Home Improvement” opposite it. “Mad” is averaging an 11.1 rating, 17 share in Nielsen, and figures to face tougher competition beginning Nov. 25, when “Coach” moves into its time period on ABC. NBC has also extended renewals to two other first-year series, the Sunday combo of “Secret Service” and “I Witness Video.” Three of the web’s nine new series have been canceled and a fourth, “Rhythm & Blues,” has been placed on hiatus. Separately, NBC said that “Blues” will be preempted this Thursday–a week earlier than originally announced–to make room for a double run of “A Different World,” including a politically themed episode of the program that was to have been delayed until later this season. NBC said the episode was re-scheduled after changes were made to capitalize on the upcoming presidential election. Thursday is also the first night of the November sweeps.