Hey, try changing the settings in "optiions > gameplay" on how the loot is displayed once it drops... you can select it to show for 10s or u need to press a key(alt is default) to show them.
hope this helps.
Should of read the full post. He clearly states that he knows about the ALT key.
@meintool I have no idea how to fix this. Try to reset all your options in battle.net (Battle.net > Diablo 3 > Game Options > Reset in-game options).
If it persists file a support ticket.