I had the same MP4. I still not found a working FW for it. Luckily I found that it can be recovery by flash 2 FW files respectively. It sound strange but it work for me.
First, Flash your MP4 with this file.
http://www.uploadd.com/download.aspx...D3221NSISI6RK9[ASNA4M
After flash, your MP4 should be show white screen. PC can detect your MP4 as USB disk.
Second, Flash it with this file.
http://www.uploadd.com/download.aspx...UH5GM5SVA1QJ8U
Then you are done. Now your MP4 should show sand watch for a while. Please wait.
The software I used is "MP3 Player Product Tool 5.11".