This is what your section in log should look like
I 11:45:02 Destination Device: [0:0:0] PIONEER DVD-RW DVR-111 1.29 (K:) (USB)
I 11:45:02 Destination Media Type: DVD+R DL (Disc ID: MKM-001-00) (Speeds: 2.4x, 4x, 6x, 8x)
I 11:45:02 Destination Media Sectors: 4,173,824
I 11:45:02 Write Mode: DVD
I 11:45:02 Write Type: DAO
I 11:45:02 Write Speed: 2.4x
I 11:45:02 Link Size: Auto
I 11:45:02 Test Mode: No
I 11:45:02 BURN-Proof: Enabled
I 11:45:02 Optimal L0 Data Zone Capacity: 1,913,760
I 11:45:02 Optimal L0 Data Zone Method: Copied From Original Disc
I 11:45:26 Filling Buffer... (20 MB)
I 11:45:27 Writing LeadIn...
I 11:45:28 Writing Image... (LBA: 0 - 3697695)
I 11:45:28 Writing Layer 0... (LBA: 0 - 1913759)
I 12:05:24 Writing Layer 1... (LBA: 1913760 - 3697695)
you entered a user specified
you should have just used the.dvd file and let ImgBurn use calculate optimal in write settings.
there is also a firmware update to your drive
http://support.benq.com/files/storage/Firmware/DVDRW/DW1620/B7W9.zip