Acer Internal DVD RW Drive not working for "written" dvds.

The Laptop is Acer Travelmate 4650. The DVD RW Drive is not working for certain kind of CDs and DVDs. If we put the orginal disk "the punched one" normally it works. Very rarely it works for a written disc. All I told is the case of reading. Writing never works. This was working in the past. The drive is trying really hard to do the Job both reading and writing which we can hear from the rotating sound. At the begining when it was working fine, it was quiet. Most of the times it will start writing and in the middle things will go wrong and it will ruin the disc. Please let me know if you have some info.