This has happened to me, where the RRoD comes up, goes away for a week and then comes back for good. But that had nothing to do with the power going out - it just happened on its own. I am hoping that the power going is what caused, the poster above seems to have it happen to him a few times with no future issues.
Your idea regarding the box is well taken though, good call since it doesnt cost me anything, may do that while playing this evening.