The Android emulator does not work properly with snapshots:
http://code.google.com/p/android/issues/detail?id=27524

One workaround to this would be for the plugin to copy away sdcard.img at the time it creates the snapshot, then copy it back when it loads the snapshot. (E.g. sdcard-snapshot-jenkins.img)
Another option would be to recreate the sdcard.img each time before starting the emulator, since it's always blank when the plugin creates the snapshot, using mksdcard 128M file.img