THE BREAKDOWN LANE No one has their finger on the pulse of modern marriage and family the way that Jackie Mitchard does. In THE BREAKDOWN LANE, she once again brings to life the drama of ordinary people going through extraordinary times.    Giving advice is what Julianne Ambrose Gillis does for a living-- every Sunday she doles it out to clueless people she doesn-t know, in a column in her local Wisconsin newspaper. But when it comes to her personal life, Julie seems to have no insight whatsoever. She has worked very hard to keep her marriage fresh and to be a good mother, so it-s a mystery when Leo, her husband of twenty years, decides to defect from their life together and their three children, Gabe, Caroline and Aury.    In his absence, Julie is diagnosed with a serious illness, which drives her children to undertake a dangerous journey to find Leo-- before it-s too late. But what they discover about their father is even more devastating than their mother-s deteriorating health.    As the known world sinks precariously from view and leaves them all adrift, the Gillis clan must navigate their way through the trenches of love, guilt and betrayal, back to solid ground and a new definition of family.