You can try updating it from usb drive.
Manually Updating the Software Using a USB Flash Drive
1. Create a directory folder on your USB Flash Drive called UPGRADE.
2. Copy the software .dlm file to this directory.
3. Insert the USB Flash Drive into the USB host port of the printer.
The software upgrade process begins.
4. When the software update completes, the printer restarts.
I'm trying to do a firmware upgrade using the web interface on a Xerox 6700DT.
It is currently at 081.140.102.24402, I'm trying to apply 081.140.103.22600. About 30 seconds after I hit the 'Install' button, I get 'Unable to process your request'.