Shooter demo minimizes immediately when full screen is selected

I built the Windows package for the shooter demo (unmodified, default settings) and it ran fine in windowed mode, but when I switched to full screen (and full rez) the screen went black and then it minimized to the toolbar. When I try to switch back to it by either clicking the icon in the toolbar or with alt-tab, sometimes it shows the menu for a second and then minimizes again.

Anybody have any ideas about this? Also, anybody know what ini file or registry settings to change to set it back to windowed mode, because everytime I try to run it now it trys to run full screen?

Configuration: Windows 7 Ultimate 64 bit, AMD 7850 w/driver version 13.152, Intel i5 3570K, 16GB

I don’t have any ideas about the problem but to get back to windowed mode have you tried to change the FullscreenMode entry in the GameUserSettings.ini, my path is:
GAMENAME\WindowsNoEditor\ShooterGame\Saved\Config\WindowsNoEditor\GameUserSettings.ini

FullscreenMode=2
If you also want to change the resolution (1024x768, 1280x720 or 1920x1080)
ResolutionSizeX=
ResolutionSizeY=

@jmr: Thanks for the ini info.

More info, when I run it full screen the log fills up with lines like these:

[2014.03.23-01.23.47:332][194]LogD3D11RHI: IDXGISwapChain::SetFullscreenState returned 887a0022; waiting for the next frame to try again.
[2014.03.23-01.23.47:348][195]LogD3D11RHI: IDXGISwapChain::SetFullscreenState returned 887a0022; waiting for the next frame to try again.
[2014.03.23-01.23.47:364][196]LogD3D11RHI: IDXGISwapChain::SetFullscreenState returned 887a0022; waiting for the next frame to try again.

Same problem here. No idea why. Alt + Enter makes it full screen but it gets minimised every time and i have to force quit the game.