I have that problem, but since I only have the remotes that came with the boxes being able to change them to a pair with no clashes isn't something I've been able to do.
And, oddly, from time to time my MBtwin (which has a card flap over the IR receiver so that my et8000 doesn't affect it) sometimes "locks-up" and won't respond to power on - but when this happens I can start it up with the "<<" key on the et8000 remote.
This is what my menu look like. The dreambox remote control entries are nothing to do with which remote I actually have.
RC_menu.jpg