Any ideas?

Did you run a mod?

Nope

If it's error code 5 with the launcher, it got corrupted somehow through coding magic. It's a fairly straightforward fix where you have to redownload the launcher.

Copying from the first hit I see on a quick google search: Error Code 5

Worked like a charm, thank you!

This problem started to happen again, seems like redownloading the launcher was a temporary solution.

I had this happen to me for while. As a temporary fix you can can go to the file in the error message
(C:/Program Files (x86)/Minecraft/tmp/tmpLauncher.tmp) and rename the tmpLauncher.tmp to tmpLauncher.exe. Then run it as you would any other program. It'll download the launcher again and then run it. Trouble is that you seem to have to go through this every time.

The only thing I could find that seems to fix it permanently was to uninstall minecraft then download the new launcher from here .

Uninstalled minecraft and downloaded the test launcher from the link you posted

Also it moved the tmp and tools folders to the desktop by itself

https://minecraft.net/en-us/download/alternative

^ if that doesnt work for you .

i had exact error , what worked for me was using http://launcher.mojang.com/mc/launcher/win/703e21de391ba20ebee6fae3a694d0b7514febb5/MinecraftLauncher.exe
which was listed in the nativelog.txt with the error . gl

p.s. i would do a full delete then reinstall from this link , or atleast thats the steps i did .
backup any logs or ss u wanna keep of course first.