Now that you mention some other apps malfunction I want to add that it all started with Wazapp not being able to resize pictures before sending them. Then, one day all contacts were lost and pictures were not shown in N9 Gallery. Fortunatelly they still were in Wazapp picture folder. I had to recover all contacts from my email account where they were backed up. Now, the interesting question: did the reset of N9 solve the problem?