Many of apps have disappeared from the main screens. On investigation I find they were all on the phone memory - the ones still working are all on the SD card. In app manager they are in the list of downloaded apps but are greyed out, and most of them start with an odd name such as com.android.... or just com... eg com.prey which I don't recognise. Even more odd, the browser has disappeared too. That' was pre-installed and I can't see anything relating to it in that greyed list. Similarly play store has gone. I'm using a Galaxy Note 1 with Android 4.1.2. Can anyone tell me what's happened please?