The error you have indicates an incompatibility between the version of bootmgr you are using and the \boot\BCD configuration file.
How do you create or modify the BCD?
You helped me to find the problem ...
I don't know WTF but the active partition was on (hd0,2) and then ... the \boot directory on D:\
Then the problem is now solved.
To update grub4dos, just replace the \grldr file with a later version.
Anyway i have a last question (it's maybe out of the topic) but why in the archive of grub4dos ( http://grub4dos.chen....6a-2016-04-10/) there is no program to install the MBR part. The only executable files are (bootlace.com, bootlace64.com, hmload.com, badgrub.exe, grub.exe ) and all return: " ...... is not compatible with the version of Windows you're running. Check your computer's system information and then contact the software publisher."
These programs seems useless but side of this, i need to download a third party program (as grubinst) to finally install the Grub4Dos part in the MBR -> I really don't understand the logic ...
Edited by islogged, 11 April 2016 - 05:06 PM.