http://bugs.winehq.org/show_bug.cgi?id=35405
--- Comment #6 from Ken Thomases ken@codeweavers.com --- 0009:trace:d3d:wined3d_check_device_type wined3d 0x1889e0, adapter_idx 0, device_type WINED3D_DEVICE_TYPE_HAL, display_format WINED3DFMT_B8G8R8X8_UNORM, backbuffer_format WINED3DFMT_UNKNOWN, windowed 0x1. ... 0009:trace:d3d:wined3d_check_device_type Unsupported display/backbuffer format combination WINED3DFMT_B8G8R8X8_UNORM / WINED3DFMT_UNKNOWN.
Seems like a wined3d bug, I think. dlls/wined3d/directx.c:wined3d_check_device_type() has a number of checks of the display and backbuffer format. For several of the checks, the comment says the restriction only applies for full-screen mode but the check doesn't take windowed vs. full-screen into account. The game is using windowed mode, but a supposedly full-screen-only check rejects the display/backbuffer format combination.
In fact, that function has a check which specifically allows WINED3DFMT_UNKNOWN in windowed mode, but the subsequent logic makes it impossible for that to pass.