While fighting a Barako boss in Valhelsia 3.4.1, he went to do his sun attack when I was right above him and this happened...the entire game's graphics just glitched (stock pack except for FTB claiming mods, no Optifine or other graphics mods). This persisted all the way out to the menu, disconnecting left me with no multiplayer menu, just a dirt screen where the icons should be.

(NOTE: Green haze is meka suit vision)

Which "sun attack" are you referring to? The supernova?

I assume so, it looked like it. It happened instantly so I couldn't really see what was going on anymore.