It crashes when I go in a minigame or switch texture pack

Hi,
Since the launcher update yesterday, I cant play anymore with my friends. When I log into a server, it works fine. But when I choose gamemode (skywars, survival games, etc.) it crashes. I have tried to reinstall Minecraft several times, and restarting my computer, but it doesn`t just work. My friend have the 1.6.76 version of the launcher, but I use the new version. I am very sure that it has something to do with the launcher. I tried to search for downloads to the 1.6.76 version of the laucher, but I didn`t get any links to downloads.
Please help, thanks!