Nokia Lumia :: 900 Screen Not Responding?

about 1 month back, my lumia 900 has the following problems : screen not responding, screen becomes sensitive (things moving by itself etc), soft resetting brings a funny problem, screen scrolling by itself and goes to settings of applications, won't stop until i did another soft reset. i have to soft reset few times for the phone to be stable.then i did a hard reset abt 3 weeks back. reinstall everything, the applications. the phone was stable but last week faced the same problems i mentioned above. i brought the phone to nokia service center and explained everything. got it back last weekend. i asked what they did. They only updated back the firmware (which i could have done myself via zune).unfortunately today, i faced the same problem. Quite frustrated as i expect quality from Nokia. don't know if this is a hardware problem or s/ware. if i bring to nokia service center, they maybe do another firmware reinstallation. really hope from some insights from nokia.with lumia 920 coming , the resale value will surely drop. i will be forced to let go the phone if problem cannot be solved and suffer a big drop in second hand value.