One of my players was complaining of an "invalid item" after attempting to skin a gun.. After a long and troublesome investigation, we discovered the cause.  

I'll try to explain...  

In this case we'll use the AK47.  Place the gun in the Upper Left box (like you would to skin the item)... Then all the skins show up... Drag ANY skin from the skins page, over that top left box. (where you placed the unskinned item)  It now makes that item an "invalid item" and can't be removed from "skins"... The only thing to do is Close Skins...

The item will now show back up inside your inventory, and can't be used, reskinned, thrown away, or anything.  The only way i've found to get these "invalid items" removed from mine or my players inventory, is to use the Player Administration plugin and "clear inventory" which removes all their items..

Can you please take a look and see about a fix for this?

Thanks
James