I seem to be having a similar problem. Trying to burn Verbatim D/L +R disks. I set the burn speed at 1X but the writing is done at 2.4X. Fortunately the disks work ok but I'd prefer the slower burn. Just for fun I tried a mini dvd (1.46)in the same Panasonic SW-9574S drive and it burnt at the speed I selected (1X).
I've attached logs of both burns.
Thanks
I 15:03:33 ImgBurn Version 2.1.0.0 started!
I 15:03:33 Microsoft Windows XP Professional (5.1, Build 2600 : Service Pack 2)
I 15:03:33 Initialising SPTI...
I 15:03:33 Searching for SCSI / ATAPI devices...
I 15:03:33 Found 1 CD-RW, 2 DVD-ROMs and 1 DVD?RW/RAM!
I 15:03:45 Operation Started!
I 15:03:45 Source File: C:\Documents and Settings\snnorlaxx\Desktop\Blitz.The.League.USA.XBOX\nflblitz.dvd
I 15:03:45 Source File Sectors: 3,762,528 (MODE1/2048)
I 15:03:45 Source File Size: 7,705,657,344 bytes
I 15:03:45 Source File Volume Identifier: XBOX360
I 15:03:45 Source File Implementation Identifier: Daikin U.S. Comtec Lab
I 15:03:45 Source File File System(s): ISO9660, UDF (1.02)
I 15:03:45 Destination Device: [1:0:0] MATSHITA DVD-RAM SW-9574S A100 (D:) (ATA)
I 15:03:45 Destination Media Type: DVD+R DL (Disc ID: MKM-001-00) (Speeds: 2.4x, 4x)
I 15:03:45 Destination Media Sectors: 4,173,824
I 15:03:45 Write Mode: DVD
I 15:03:45 Write Type: DAO
I 15:03:45 Write Speed: 1x
I 15:03:45 Link Size: Auto
I 15:03:45 Test Mode: No
I 15:03:45 BURN-Proof: Enabled
I 15:03:45 User Specified L0 Data Zone Capacity: 1,913,760
I 15:04:06 Filling Buffer...
I 15:04:07 Writing LeadIn...
I 15:04:08 Writing Image...
I 15:04:08 Writing Layer 0... (LBA: 0 - 1913759)
I 15:23:59 Writing Layer 1... (LBA: 1913760 - 3762527)
I 15:43:11 Synchronising Cache...
I 15:43:15 Closing Track...
I 15:43:16 Finalising Disc...
I 15:45:05 Image MD5: c2b7461d6679e8eb79643ef488474fa0
I 15:45:05 Operation Successfully Completed! - Duration: 00:41:20
I 15:45:05 Average Write Rate: 3,213 KB/s (2.3x) - Maximum Write Rate: 3,779 KB/s (2.7x)
I 15:58:30 Close Request Acknowledged
I 15:58:30 Closing Down...
I 15:58:31 Shutting down SPTI...
I 15:58:31 ImgBurn closed!
I 20:08:55 ImgBurn Version 2.1.0.0 started!
I 20:08:55 Microsoft Windows XP Professional (5.1, Build 2600 : Service Pack 2)
I 20:08:55 Initialising SPTI...
I 20:08:55 Searching for SCSI / ATAPI devices...
I 20:08:55 Found 1 CD-RW, 2 DVD-ROMs and 1 DVD?RW/RAM!
I 20:09:22 Operation Started!
I 20:09:22 Source File: G:\GC\Zelda\ind-tloztp.iso
I 20:09:22 Source File Sectors: 712,880 (MODE1/2048)
I 20:09:22 Source File Size: 1,459,978,240 bytes
I 20:09:22 Source File Volume Identifier: The Legend of Zelda Twilight Princess
I 20:09:22 Source File File System(s): None
I 20:09:23 Destination Device: [1:0:0] MATSHITA DVD-RAM SW-9574S A100 (D:) (ATA)
I 20:09:23 Destination Media Type: DVD-R (Disc ID: RITEKG04 01) (Speeds: 1x, 4x)
I 20:09:23 Destination Media Sectors: 714,544
I 20:09:23 Write Mode: DVD
I 20:09:23 Write Type: DAO
I 20:09:23 Write Speed: 1x
I 20:09:23 Link Size: Auto
I 20:09:23 Test Mode: No
I 20:09:23 BURN-Proof: Enabled
I 20:09:26 Filling Buffer...
I 20:09:27 Writing LeadIn...
I 20:09:45 Writing Image...
I 20:27:28 Synchronising Cache...
I 20:29:42 Image MD5: 41deff9b1fd2831f48fbfa2dd1054e4d
I 20:29:42 Operation Successfully Completed! - Duration: 00:20:19
I 20:29:42 Average Write Rate: 1,341 KB/s (1.0x) - Maximum Write Rate: 1,417 KB/s (1.0x)
I 20:49:54 Close Request Acknowledged
I 20:49:54 Closing Down...
I 20:49:54 Shutting down SPTI...
I 20:49:54 ImgBurn closed!