Sometimes, the data files are "damaged" due to the internet connection disrupt. Keep a copy of each data files and just replace the damaged one and update the information via internet.
Based on my understanding, when you tap the update button, the program will delete all the previous data and rewrite all of them with new ones. The problem is, if there is a internet connection problem, the data file will be empty. The developer will try to address this issue in the next releasing. For now, just like jacwolf suggested, re-copy the whole folder and reupdate the information.