This has never happened to me before, yet tonight several times now in the middle of just farming around Wrothgar randomly killing stuff and picking flowers on my Sorcerer, I suddenly cannot loot anything. I can attack, target things, use abilities, etc. There is no lag (latency at 130ms all three times it happened).
The only fix is a complete reboot of the game (reloadui does NOT fix the problem).
This is, as you can imagine, incredibly annoying! Is this something introduced with the last patch? I haven't updated addons or anything so I can't imagine what else it might be.