My is doing the same thing now. It first stopped syncing and gave "The last sync failed. An error occurred while Mapping Handling. You may want to restart FTM and start again."
I have tried all the usual; virus firewall malawarebytes shutdowns, compacting the files, rebooting, to no avail.....
This is just so irritating and they have not done any updating for ages. I am running Vista, but have not had an issue before, except when one of their techs told me to do "control F5" to download all the images, and that really screwed it up and it lost the file and I had to reload from ancestry.com (my tree).