There is an option somewhere that the phone will go silent if turned face down...you know good if you enter a meeting. Perhaps this is what is happening?

I wish this feature worked for me but my custom kernel prevents its function.

 

Hi;
there is many things that can turned on silent mode ;
-If this is some how accedently happening in your pocket, so i'd suggest setting an unlock pattern.
-or if you turn down the ringer volume the whole way it turns on silent mode..

i think that you might try an app that allows the creation of sound profiles for phone ring and notifications. profiles are outdoor, silent.. etc ,its the Night Ringer app I heard about before and i think this should solve this problem

Java Programming

 

I am having the same issues but its in 2~5 sec
it will auto-change it to silent mode on but not even the vibration will be turn on
btw my vibration is set as away on
and i turn off the "turn over" motion too....
so basically I wouldnt be able to see the phone ring other then putting the phone on my face to see the phone is lighting up cause by the incoming call...

can anyone solve this problem?

 

I'm also facing this problem but not that much...still wanna know the solution.

 

I am also facing this problem. I just feel the buzz of my phone while its lying on its back face up. When I check the phone I find that it turned itself into silent mode. I didnt face this problem earlier when I bought my Galaxy S2. I started getting this problem when I started using Voxer (walkie-Talkie app) actively. What I also noticed is that when I turn my phone into silent and put it in my pocket, it turns into non-silent mode also by itself. Weird problem. Could this be the reason or is it just a coincidence? Can somebody help me please? I would greatly appreciate it.

 

did you find a solution to your problem? I am facing the same problem and it is pretty annoying..Can you help?

 

I have the same problem! Did anyone find a solution to this?? I cant find answers anywhere

 

Check the details in under the 'Power saving options' settings.