Hi redruM69;
The FVMAIN.fv let you recover the firmware but when you update it, you get an error, right?
Is something stopping the update process, network connection or something wrong with the IDE (closing the program or something related)?
You could try to re-install the drivers maybe it could be an issue with the port (be sure to select the port and board in the IDE), are you using a 3.0 or 2.0 USB port?
Regards;
CMata