I have a Sony DRU-830A dvd burner that worked a while ago. For some time now I've been trying to burn dvd's but end up with coasters. At this point, the drive can read and play CD-ROMs and will play DVD movies. It will NOT read data dvds or burnt dvds. It will not burn DVDs anymore. I've checked the firmware and its up to date. It shows no problems in the device manager. I don't know where else to look. Any suggestions would be appreciated.