I must add that I also experienced this problem. Not long after Deme noticed it, I believe.
I left RPworld and when I returned, found that I'd lost an enchanted Diamond Sword, an enchanted Bow, a Diamond Pick, about a stack and a half of arrows and an Instant Health II potion. There was other stuff in my inventory, but I can regain that fairly easily.
EDIT Many thanks to Deme for restoring my items.