Ubizmo
Newbie
I've been having the same problem and I've found out it was because my memory card was failing. I had set it to use ring tones that were on my card. I also found out that it was draining my battery rapidly probably as it was trying to access my card
That's not the problem in my case. I moved the files to device memory and the problem still happens. I think it's a bug in ICS. It's not that big a deal for me, just a minor annoyance. Those who are losing notifications and ringers altogether have a much bigger problem.