I too am having sync problems with FTM for Mac (os=10.7.3).
I have had the application for about 1 month and after the initial sync, I have had a number of issues, similar to the problems described.
Today, I have unlinked from the online system, uninstalled the app and reinstalled. All to no avail. I think I have corrupt data, but I'm not sure how to delete it.
(I purchased the app for its supposed reporting ability - but so far, bad data leaves me frustrated.!)