Great, I forgot to copy the error before I closed it. Oops!
So, I'm an orc fighter in the lost ruins of horrendous mist. Just hit level 5, and I killed two things that dropped gold right beside one another. I picked up 35 gold pieces, stepped left - into an open doorway, and attempted to pick up 30 gold pieces. I got an error that resulted in my pile of gold pieces in my inventory disappearing.
Two times when i picked up gold (don't know if it was dropped) i also got a controlled error:
at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
at java.util.AbstractList$Itr.next(Unknown Source)
After continuing the pieces of gold were added to the stash in my inventory (at least i think so; i didn't calculate it) .
But one or two other items which i had picked up before were missing.
I picked up gold before and after that without an error message.
I got the same thing, picked up some gold then got an error message. The gold was gone from the floor, but most of my stuff (not all, and not anything I had currrently equipped) had disappeared from my inventory.