I have a program working in the Android Emulator. Every now and again I have been creating a signed .apk and exporting it to my HTC Desire to test. It has all been fine.
I had the same issue, i.e. App showed up as being installed, but would not launched when the icon was tapped. After some head-banging, I found that I had stupidly placed ' android:exported="false" ' for my main launcher activity within the AndroidManifest file.... Once I removed it, the App launched fine..