An overheating problem among drives used with new high-speed discs can destroy both the unit and the medium, manufacturer Pioneer is trying hard to avoid saying. Using soon to be available 4X discs for DVD-R and 2X discs for DVD-RW with the following drives is thought to be risky: DVR-7000 DVD recorder; PRV-9000 Professional DVD recorder; DVR-A03 computer drive; DVR-103 computer drive; DVR-A04 computer drive; DVR-104 computer drive. There is a firmware update available, along with the company's intentionally-vague bulletin
In addition to the items mentioned, several OEM units are affected, but Pioneer won't say which ones. You'll just have to contact your box builder and ask them if they have a fix.
Keep in mind that the discs currently on the market won't cause the failure. But you do have to apply the firmware fix before using the newer, faster ones to avoid the inconvenience of smouldering equipment.
News source: The Reg
View: The full story
View: Pioneer DVD-R/RW bulletin
Download: DVD-R/RW firmware updates