In MIX, click on File, then Return.
Then Security at the very top, and Clear Cache.
Click on the Clear FORMS cache and then log out and log back in
THEN click on the Clear TABLES cache and log out and log back in
and finally, click on the Clear TREE cache and log out and log back in.
You do have to log out after each one (it won't prompt or make you, so you have to manually do it).