It's shift+tab, not alt+tab
Did it work for you with shift+tab? It worked for me.
Sorry, I meant shift+tab. And no. Just tried again and still nothing.
Do you have a console output from steam?
I've got the 'log' in the OP.
Ah, sorry for missing that. You're running the 64-bit version of the game and there's no 64-bit overlay support. You could edit the coe launch script to launch the 32-bit version, or ask the game developer about an option.
The 64-bit overlay support feature request is #519.
Also can't use the 'copy key to clipboard' function to paste CD key in
Log
System info
Edit: tried using '-opengl' launch option which worked with similar issue with Dungeons of Dredmor, but this causes the game to fail to start at all.