Android - Unknown Error code during application install: "-24". I upgraded my phone to CyanogenMod and was getting this error when trying to reinstall CardDAV Sync (I don't use Google for my contacts, I use Owncloud on my own server.) Turns out the solution was to enable "root mode" in my filemanager then go to data/data/ and find the carddav directory, deleting the file inside. After that it installed fine without error.