I don't believe it's a hardware issue more than its a network server issue. Remember these items we hold, all of them, are not stored locally on our systems which is why there is no save file. This is evident in when you first open up your menu and all the other non equipped guns and items don't pop up immediately. It's possible that increasing the vault size to much would make the user suffer load times or some sort of memory issue. Just an educated theory. So until they work around this problem I say be happy. Or play borderlands, that game is soooo much fun.