I have a multi GB collection of images that I sync between two computers. The images are synced correctly, but there are always a few MB of data remaining that do not transfer (correctly reported on both machines). I have discovered that the remaining files are hidden ".picasa.ini" files located in each directory. The total number of these and the their size seem to match what Sync is reporting as pending. Not sure if it will help you, but it seemed to be a similar problem.