Hi lumax,
I've got the same error as you. So I copied Pioneer Update firmware V3.021 files with it's WINCE files to SD card, and tried "Upgrade from SD/USB (formated)" in service mode. So, it says - "Image Read 100%, then Write Image 100% - Restart your machine". When I turn it off and on again - it does not start white screen with update procedure.
Could you please describe what you've done exactly to fix this problem? Or maybe someone else know?
Thank You!