Update failed: Unspecified error

I was having the same problem , and maybe is a firewall blocking the updates or maybe you anti virus or anti malware blocking some files while downloading (remember the anti virus or anti malware its OK with the old version of league but not with the new one ) i fix this problem today and i just used orbit uninstaller and uninstalled the anti virus (risky) and ran like admin and boom the error did not popped up at 32% yay! , if this works for you and you can download the game plz contact me in game (DarkLonus) Thanks and Good Luck!!

(bare with my English)