Update: Rebooting the PC fixed it, not sure why that helped, though.

The launcher auto-updated to 1.6.76, and all I get for a launcher is a white box, minecraft icon in the title bar, no title, and that's it. This is the nativelog.txt file

D:\Program Files (x86)\Minecraft\nativelog.txt
Set run directory to D:\Program Files (x86)\Minecraft
Native Launcher Version: 1157
Operating System: Windows 7 Ultimate
Application Hash: 59395b36c0dc80a005337acec4c407dd57dfe389
Application Data directory: C:\Users\Kirk\AppData\Roaming/.minecraft
Executable Path: MinecraftLauncher.exe
App Directory dir: D:\Program Files (x86)\Minecraft
Start dir: C:/Users/Kirk/AppData/Roaming/.minecraft
Launcher dir: D:/Program Files (x86)/Minecraft/game
TmpDir dir: D:/Program Files (x86)/Minecraft/tmp
(Optional) Java Launcher hash:
Java Version: 1.8.0_25
x64: 1
LauncherConfiguration from: http://launchermeta.mojang.com/mc/launcher.json
Downloaded config
Native launcher is current
Native launcher is current
Loaded upgrade id: 693935801
Using new launcher as we're in the rollout!
Launcher library is up to date with hash 7cb412e4765071f4a084fc2252538c01ee80b56
3
Check to see if we can run the launcher
Native launcher is current
Starting launcher.dll with D:\Program Files (x86)\Minecraft\runtime\jre-x64\1.8.
0_25\bin\javaw.exe
Found SetDllDirectoryW in kernel32.dll!
Added D:\Program Files (x86)\Minecraft\game to DLL search path
Running launcher!
Launcher ended with 0
her.dll on child subprocess: 183
Couldn't open launcher.dll on child subprocess: 183