Quote from gerbil
You have an adblocker that is preventing the download of some resources whose URLs contains the path "/ad/"
One of the sounds is for glass breaking. You'll get a crash when MC tries to play the missing sounds.
You'll need to figure out how to configure your adblocker to whitelist http://resources.dow....minecraft.net/
edit: The April fool version had more sounds with hashes that start with 'ad', like snow4.ogg, yes3.ogg (a villager sound) and calm2.ogg (music)
Disabled Kaspersky, reinstalled everything - works perfectly. no more splash pots crashing my game.
I want to thank you A WHOLE BUNCH! Sir.