can't get my iphone 3 to synch anymore

My iphone 3 worked fine for about a year, then I must have upgraded something.  Now I get this error message:  "The iPhone “xxxxx’s iPhone” cannot be used because it requires iTunes version 10.6.3 or later. Go to www.itunes.com to download the latest version of iTunes."  My pictures synch, but nothing else-- no music, notes, contacts, calendar-- nothing.  I know lots of other people have had this problem, since i've seen lots of complaints about it.  Has anyone solved the problem?  I use a mac, in case it matters.  Thanks.