I went through a period of time where my phone didn't ring, vibrate, or anything. When I was finally scrolling through my ringtones trying to get one to play, I got the popup message "All Sounds Off Mode Selected". WTF? So, I somehow got into this mode. With the help of a googled forum post, I found that when that popup was visible, if I fiddled with the volume buttons I would get a control that allowed me to select a variety of modes, from all off to vibrate only to some others that I haven't yet tried yet. Not sure how I got in that mode, but it's clearly not accessable through the tools menu! Here's the link, which isn't exactly clear on exactly what mode this works in, but it was enough info to stumble into the solution:
http://www.fixya.com/support/t1425040-turn_samsung_juke_all_sounds_off_mode
