Which firmware do you currently have on board 1.xx or 8.xx?
If it is an 1.xx series firmware, then make sure you are using the correct flasher! You should be using the DVRA12J_FW128EUJ.EXE firmware file from here: http://pioneer.jp/device/dvr_a09.html
If it is a Buffalo OEM 8.xx firmware I suggest you download the PIONEER DVR-A12L (DVR-112L) A12L_115.zip firmware file from TDB and use it to crossflash your drive to a Pioneer 1.xx retail firmware, and then you use the official 1.28 to update your drive to the latest available firmware.
I almost forgot to say that because the TDB firmware is a RPC1 one the official DVRA12J_FW128EUJ.EXE will likely refuse to flash your drive because it detects it as RPC1. In this case you need to unpack the DVRA12J_FW128EUJ.EXE using WinRar or a similar archiver program and then use MCSE to patch the UPGA12L.exe flasher file by ticking the 'allow like with like flashing' box and then saving the patched flasher. Since you're at it you might want to also patch the firmware file (A0413431.128) ... once you have the speedpatched file, delete the original and rename the speedpatched one as A0413431.128 and then use the speedpatched UPGA12L.exe flasher to update your drive.
The 112L drives can have either a proper Pioneer 1.xx firmware on board (DVR-A12J) or a Buffalo OEM 8.xx one ...