NBC is diddling around with their schedule - starting some shows a minute early, expanding some half-hour shows to 31 minutes and essentially just pissing off anyone with a TiVo or VCR (I'm one of the lucky ones with a two-tuner TiVo, but for most of America, this is a royal pain if you want to tape/TiVo something which overlaps this dorkfaced idea).
The always-brilliant Mark Evanier will fill you in on the details at his blog. While you're at it, check out his POVOnline site (link fixed). Mark's a prolific and highly respected cartoon and comic writer 'round these parts, and between his two sites, you can get lost for several days.