The upgrade from Java6 to Java7 over the weekend was always going to cause me some headaches. One of them seems to be signing jar files to install on Android. On closer inspection Android doesn’t really support Java7.
So, the jarsigner needs a little tweaking in order for it to work:
jarsigner -verbose -sigalg MD5withRSA -digestalg SHA1 -keystore [keystorename] [nameofapk.apk] [username]