I have a problem with mine also, it's very annoying with writing a long message. My screen just goes black and I need to flick it to get it going again... does it alot. I think it started after I started using the slider in a flicking motion (letting it jump back after).

I had to put some tack in it to keep it constantly in the on position... now my phone works (no blackout) again but I have no more slider. So annoying.