ORIGINAL: russtbird
I'm surprised nobody has offered any knowledge on this one, given the regular discussion over RMS and a few other faults.
A colleague of mine had a similar experience with his '03 3.2S after 1yr & 12k miles; he heard a metallic rattle - once when out on the road & once again as he was putting the car away for the day. He came out to the garage in the morning and nearly slipped over on the oil slick which had spread all over the floor. Turned out to be a broken main shaft(??) if I have described it correctly. OPC replaced the engine for him after a bit of persuasion.
I remember one of the other Boxster (female I think) owners has reported something similar to your problem too - a search might turn something up.
I can only hope this is not your problem & wish you luck. Let us know the outcome.