Unable to upgrade Firmware

[SAMSON]

Hi folks,
I have been browsing this forum for about 1 month and until now, I was able to solve all my problems simply by doing some research etc.
But this time, I habe have been searching and searching for quite a long time, yet I couldn't find an answer.


So, here it is, my damn problem:

I extracted the F/W of my MP4 Player and corrected some Strings (doing a proper translation, correcting the german messages) as well as changing several images (welcome animation, battery status).
But now, I can't upload the modified firmware to my mp4 Player. Everytime I choose the firmwarefile and click the "update"button, i receive a message telling me "Open upgrade firmware file error!"


Here are some more detailed pieces information:

mp4 Player: http://www.kingzon.de/de/pro/Multimedia/MP4/M4XGP.html
FW-Version: 9.1.52 (Release date 09.01.2005)
Manufacturer: Wilson Co. Ltd.
MTP Manufacturer: Actions Semiconductor Co., Ltd.
MTP Version: V1.00.3333
F/W extracted and modified with s1res v3.60
Tried to upload F/W with "mp3 Player Upgrade Tool" from the "mp3 Player Utilities 4.15" Suite

Thanks in advance for your help,
samson