Lemme think off the top of my head here on a few of these. 2006 - Ran through September, including road win at Syracuse. Beat Illinois to open Big Ten season. Got trucked by OSU the next week. Throttled Purdue the following week and didn't win another conference game the rest of the year. Tate was dinged, though. Tate was better for the bowl game and Andy Brodell kept us in that thing. A freshman Colt McCoy prevailed at the end of the day, however.
2007 - The Fat Cat team. Stunk most of the year. Got rolled by Western Michigan on Senior Day to mercifully end the season without a bowl game. Sports Information Department changed "consecutive bowl games" to "consecutive years of bowl eligibility" to put a little shine on that turd.
2010 - Team started 5-1 and melted following the fake punt Wisconsin ran. Pounded MSU (keeping them from the Rose Bowl) and looked like they regained their swagger. Then, proceeded to nearly lose to Indiana the following week before conceding 3 consecutive losses to Northwestern, OSU (in a game where we actually looked decent) and Minnesota. Did rally for a nice bowl game win, though.
2012 - I have tried to repress this one, but I think we lost 5 or 6 in a row in conference play.
Moral of the story - some years, the team has clearly shown major incremental improvement every week. 2002, 2004, 2008 and 2009 come to mind in this regard. But for each of those years, there are an equal number of years where the team pretty much collapses or doesn't really get any better.