Blizzard deployed the second patch of Mists of Pandaria beta tonight (a bit over 500MB). There is a known issue. Ultra and High settings might cause buildings and other textures be a massive flat pink cube. Changing the settings while in-game will cause a client crash.
The fix is to go to the login screen, and click Options. Change the view distance to good or fair. Then login and test if the pink squares are gone. Blizzard is likely iterating and polishing ultra and high settings.
I’t's common to see in the general chat the quest “Acid Rain” is currently bugged, and works in an out after a few attempts.
All quests where players need to gather items from the ground such as herbs, berries, scrolls, maps, figurines, etc. are currently bugged. The items are not glittering nor seen. Seems to be work in progress. This sorta halts quest progression of long questlines. Search for other quests, and run dungeons when possible to level up.