This forum is dedicated to discussions pertaining specifically to the Motorola ASTRO line of radios (those that use VSELP/IMBE/AMBE), including using digital modulation, digital programming, FlashPort upgrades, etc. If you have general questions please use the General or Programming forums.
You need the DX upgrade chip. Someone on this board should be able to help you out. The DES-XL chip you are refering to is just a plain DES-XL chip, nothing more...
Once you have the DX upgrade chip, you'll be able to load keys into the Astro Saber just fine.
I did see something on the board that said if the firmware was upgraded by mother M, then the 3011DX wouldn't work, but I don't have all the info on that.