Stuck at 640x480/720x576 resolution

[Charles McGill]

CS:GO is stuck at two resolution options: 640x480 and 720x576. I have tried the following:

Restarting my computer
Restarting Steam
C:\Program Files (x86)\Steam\bin\SteamService.exe /repair in regedit
Updating graphics drivers
Resetting AMD Crimson profile settings for CS:GO

This happened after the game (kind of) crashed: it sent me to the desktop and wouldn't allow me back into the window, apart from a small bar which appeared in the top left of my desktop when I selected the game. I could still hear sounds of the community deathmatch server I was playing at the time. I killed the .exe in task manager and re-launched the game, and it launched in 640x480.

This has never happened to me before and I haven't found any similar occurrences elsewhere.

I have tried launching other games (including source games) and I did not have any problems. Any help is appreciated.