Just to advise those who may sync multiple macs with dropbox. I was initially only syncing the "data.sqlite" file between the macs which seemed to work ok but when I tried to sync with the iphone it would not work. I have since discovered that you need to sync the "Library.mentalcase2lib" between the macs. Once I synced these folders I was able to successfully sync my iphone with either of my macs with mental case. There is obviously other files contained within library.mentalcase2lib that were required when syncing the iphone.