Launcher does not open a window after being opened

Starting the launcher creates three instances of the MinecraftLauncher.exe, all three hanging at around 0% CPU load. Actual Launcher window doesn't appear and it's stuck forever at this stage. The only logfile I can see is the "nativelog.txt" created next to the MinecraftLauncher.exe.

I have tried to reinstall Minecraft from the latest installer, it's getting installed and updated correctly, but when it tries to start after all updates - same thing happens. Initially this happened to a correctly functioning install with no apparent changes AFAIK.

This is not directly connected to MCL-5569 since I've not used NTFS symilinks, and tried reinstalling in two different locations with same result.