Whenever I try to slide to answer or slide to cancel alarms, just a touch of the "button" will allow the action. It's a pain on my alarm because I'm never sure if I hit cancel or snooze.
You will need to get your touchpad replaced. Touch pads tend to wear off and when they do so, it gets hard for you to even unlock your android. Just get it replaced, it should work perfectly fine after doing so. If it still has problems let us know.