So I tried posting this question at xdadevelopers but haven't gotten any replies. Personally, I'm kind of irritated at that forum because every question I post never gets any replies whatsoever. Anyways, hopefully someone here might have some insight into this question... So i wrote a quick small app, a media player, real basic. It scans the internal and external storage for mp3s and you start by clicking on an artist, then click an album, then click a track and then it plays. I was able to run the app in two different emulators, and then i was able to install and run it on my Huawei s7 tablet. I then gave a copy to my two friends to load onto their phones to test out, but the app won't play on the phones. One has a motorola droid and the other has a nexus 1. They installed my app using 'apk installer' (downloaded from the market), and it seems to install fine, but it has to force close when they try to run it. The option on the phones to install non market apps is enabled. I am at a loss as to why it won't run on the phones but it will run on my tablet and emulators. I can't really think of what differences there might be between the phones and tablet, except maybe screen size...?? I installed another program on the motorola droid that i wrote and the app ran fine. The apps that i have been writing have been developed using android 1.6 and the tablet and phones are running android 2.2 so its not a versioning issue. There are no permission issues i don't think. Anyone have any ideas or things for me to investigate to figure this out? I would appreciate any clues.