I Have a Samsung Galaxy S2.
I had it for around 2 weeks, when it first turned itself off and wouldn't turn back on again. The keyboard would glitch and stop working. and apps like Facebook, or Google Play, Internet etc would freeze then the error
'Application' Is not responding send error report etc.
I've just got it back from repairs, and the applications are still stopping responding, it hasn't crashed yet though. Any ideas what could be making it do this considering they've completely wiped the phone and screened it etc?