[Reyoki]

Pinkie is right. It means you have too much stuff!

It has to do with the fact that the avatar editor and the trade system draw from the same bit of coding. Coda has said a few times already that he and the other coders are working on the problem, but to completely fix it would require a complete re-write of the inventory system's coding, which would take the site being down for a couple days to implement.