I don't think you have to (or even "if" you can) assign a static IP to the Echo itself. I think Echo asks the router what IP's are available. You get whatever the router dishes out.
Maybe your router has a setting similarly named as mine, that I have enabled. My setting is called "Manually Assigned IP around the DHCP List". When this is enabled, Echo has the same IP reserved for whenever it wants to use it.
What is the model number, and firmware version, of your router? Maybe someone here has the same one, and could suggest further.
Edited by crash2009 - 12/23/12 at 12:33pm