When I download and open up des1228_fw_11102.zip, there's a readme in there called "DES-1228_A1_Release Note_FW_v1.11.02.pdf".
In the release notes section for 1.11.01 (which applies to .02, my guess), it says:
"This version (v1.11.01) only supports direct firmware upgrade from v1.10.xx. If the device is with firmware v1.00.xx, please follow up the “New Firmware Upgrade Procedure “ document to upgrade the firmware from v1.00.xx to v1.11.01. If the device is with new firmware v1.11.01, it is not allowed to downgrade previous firmware v1.00.xx."
I downloaded v1.11.01 and found the readme file in there which says to upload three files, one at a time. Then I can upgrade to .02. It looks like I have some work to do tonight, because it needs to reboot after every load.
In this order...
1228FWU.hex
1228ldr.hex
DES-1228_A1_1_11_01.hex
DES-1228_A1_FW_1.11.02.hex