I've encountered a bug that claimed two items in one of my character's inventory. When moving the item to a different bag from the current one, it would disappear and not reappear in the new bag, not reappear in the old bag when it was re-opened, nor would it after re-logging. I'm not sure if it's reproducable or not, the two items were a generic bottle of anti toxin and black fist armor.

Can anybody reproduce this, either in EfU or in the NWN OC?

I suspect that this may be a Bioware issue that we can't fix.