Please, accept our sincerest apologies for the delay in replying. If you are still interested in resolving of this difficulty, we will be happy to supply you with the needful assistance. We would kindly ask you to try upgrading SyncMate to the latest released version (4.1.1875) and testing the sync process.
In case if the difficulty persists even under the latest version, then, most probably, it is related to glitch of Mac OS sync service driver, which could be fixed by the correct restarting.
For further troubleshooting of the difficulty, please try to proceed a driver restart following the below steps:
1. Download the specific interface for Sync Service, called iSync. It could be downloaded from:http://dl.dropbox.com/u/35834399/iSync.zip
2. Extract the archive and copy iSync.app to ~/Applications folder.
3. Launch it, Sync Service icon will appear in Mac menu bar.
4. Close all other applications.
5. Hold the Option key on your keyboard and click the Sync menu in Mac menu bar.
6. Choose "Reset Sync Services..." option.
7. Reboot your Mac.
After performing of these steps the sync process should start working without a problem.
Then try to sync several times and let us know if the issue persists. Thank you.