Make sure you running the 1.00-A9 firmware. http://www.firmwarehq.com/LG/WH10LS30/files.html
Right click the drive selection box when you're in Write mode and click 'Check for firmware updates'. There you'll see the full firmware version number.
Your Pioneer has also a later firmware update. http://www.firmwarehq.com/Pioneer/DVR-218L/files.html
Yeah, SP1 for Windows 7 is out now, probably has nothing to do with the burn but you should update it anyway.
If the firmware update don't solve the problem, you should change the media for some better quality.