Maybe you are installing from a different port than a previous install. It usually happens when the update is not downloaded from the same port. For example, the first one may be named as "com.freepass" and the other named "com.freepass.eng" inside the Android/data folder. I assume you are now trying to install android ported by wills, Walkthrough mod. In that case, you will have to copy save files from android/data/com.freepass.eng to somewhere else. After installing the different port. You can again copy/paste your copied save files into new port. For example, Android/data/com.freepass.wills
Hope it helps. Have a nice day.