Problems with the 2006 Infiniti M35/M45?

I am looking at buying a 2006 Infiniti M35 or M45; however, i have heard there were some problems with these models, can anyone confirm this? If so what were your problems and how much did it cost to fix? Lastly, if there are problems would this be a bad year to buy this car? If so i will not be able to purchase any newer models because of the price listings. Thanks for any responses.