cg5660-m set top box durabrand?

used to work well so i purchased another identical box, the original one went into a sort of locked mode??, would not receive commands from the remote, so changed batteries in the remote, no luck, changed the box for the seccond one then this did the same. what the hell is going on here i thought. anyone out there had the same ?, and if so can u fix it. bob can`t and i'm none the wiser. thanks