problems with flashing dbox sagem with ftp program

hi,
i've got a sagem dbox and i have been trying to flash it with all images i could with an ftp programme.but every
time i drag and drop the image i get the following msg............................................................................<Request denied.
Please verify that the file or folder exists and that you have the necessary permissions on the server to perform the requested operation.>........................................

i have tried with a usb to serial port cable but when i use the image flashing assistent.it does not work either.
any help from anyone will be much appreciated.thank u in advance