Just for laughs, why don't you check the system for fault codes? Maybe one, or both of the seat belt buckle switches, or possibly the child seat recognition sensor, is the problem. If the control module turns out to be the problem, it's not a "plug and play" job. The replacement unit will need to be programmed. Let a dealer do it, or at the very least, a qualified independant shop. You don't want to take any chances when dealing with SRS issues.