Why doesn't Eclipse always install my APK?

I'm using the Android plugin for Eclipse on OSX, latest versions of everything. When I run or debug my app, Eclipse is very开发者_C百科 inconsistent about uploading/installing the new APK. Nothing I seem to do has any effect on this. Clean builds, debug, whatever, there seems to be about 50/50 chance of installing the APK. Or not. If not, then I have to kill the emulator and try again. What is going in?

then you in that state try from terminal adb kill-server then adb devices