Jim, the famous fictional detective Sherlock Holmes once remarked something to the effect that when you've ruled out everything else, whatever remains, no matter how improbable, must be the explanation :)
In this case the only explanations that seem to present themselves are the ones you and others have offered, the voltage spike possibility (which of course would result in a proportional current spike), and the possibility that it is all coincidence (meaning that the fuses will eventually blow on other outlets as well).
Sprink's words that "the lights have blown twice WHILE plugging in to this outlet" would seem to give credence to the spike theory, because the spike would be adding to the already large current surge that occurs during the first second or two after the lights are connected (due to their low resistance when cold). You appear to be saying that the spike would be either too brief or too small to blow the fuse, but given all the foregoing my feeling is that it is a close call as to whether that possibility or coincidence is the least unlikely possibility.
Sprink -- When you respond, it would also be helpful to know the ratings of the fuse (amperage, fast blow/slow blow, etc.), and how many lights are in series with it, and what their voltage and wattage ratings are.
Regards,
-- Al
