so glad I found this thread since I have about the same problem. Just bought the BenQ recorder which was tested quite good in a large german magazine and performed best in combination with exactly the TDK TTG02 with firmware B7P9.
My device was equipped with that firmware and I bought 25 TDK DVD-R TTG02.
But the burn process does not even start, all programs abort. Here is what DVD-Decrypter says:
I 13:20:23 Operation Started!
I 13:20:23 Source File: E:\storage\xxx.ISO
I 13:20:23 Source File Sectors: 2.285.859 (MODE1/2048)
I 13:20:23 Source File Size: 4.681.439.232 bytes
I 13:20:23 Destination Device: [2:3:0] BENQ DVD DD DW1620 B7T9 (J:) (ATA)
I 13:20:23 Destination Media Type: DVD-R (Disc ID: TTG02) (Speeds: 2,4x; 4x; 8x)
I 13:20:23 Destination Media Sectors: 2.298.496
I 13:20:23 Write Mode: DVD
I 13:20:23 Write Speed: MAX
I 13:20:23 Test Mode: Yes
I 13:20:23 BURN-Proof: Enabled
E 13:20:39 Failed to Reserve Track! - Incompatible Medium Installed
E 13:20:40 Operation Failed! - Duration: 00:00:17
I 13:20:40 Average Write Rate: N/A - Maximum Write Rate: N/A
I don't know what's going on there, so I am quite curios what happened to your BenQ.
I was about to try the writer with B7L9 firmware, but I cannot find it on the BenQ homepage, only firmwares I have are B7P9 and B7T9, which I flashed on the drive without any change.
Other media seems to work fine, although I just checked one other brand plus a DVD-RW.