Npc won't sell to me, "misplaced item"
 

NPCs on my server will buy my items without any problems, but if I attempt to buy from them, they tell me "Sorry I seem to have misplaced the item try back later." I've looked all over the code and the database and can't figure out why this is happening. I haven't modified the code involving buying items at all.

I'm reluctant to believe this is a database problem because the database I use works on other servers it is implemented on. Also, I sniffed the packets sent by the client when I had various items selected in the buy window, and all the packets were identical (which would mean the client would be not sending a slotid for some reason), however I'm extremely disinclined to believe my client is screwed up and more willing to think I just messed up when sniffing.

Has anyone had this problem and been able to fix it somehow?

Any feedback is greatly appreciated.