I found the answer. The .apk was being signed as part of the build in adt, but with a key that didn't work. For some reason the jarsigner step didn't completely replace the old signature, or show any error. So when the .apk was installed on the Android device it had a problem with the bad key. The trick to finding this was to open the .apk file as a zip file before running jarsigner, and then delete the META-INF directory. jarsigner then created it correctly, with the key Android creates in the .android directory.
-- View this message in context: http://apache-flex-users.2333346.n4.nabble.com/Problem-installing-apk-on-Android-5-0-2-phone-Certificates-problem-tp12655p12660.html Sent from the Apache Flex Users mailing list archive at Nabble.com.
