QtWebEngine crash on start-up

I've been trying to get QWebEngine up and running in my VS2013-built application, but the helper program, QtWebEngineProcess.exe, keeps crashing with exception code c0000005. I'm not sure how to debug this further, since it's a separate process.

So I tried running the Qt Examples via Qt Creator for QWebEngine: fancybrowser, demobrowser, and nanobrowser. All of them crash while loading their first page, and the crash window has the same info each time:

Problem signature:
Problem Event Name: BEX
Application Name: demobrowser.exe
Application Version: 0.0.0.0
Application Timestamp: 56c28fcb
Fault Module Name: StackHash_0a9e
Fault Module Version: 0.0.0.0
Fault Module Timestamp: 00000000
Exception Offset: 00000000
Exception Code: c0000005
Exception Data: 00000008
OS Version: 6.1.7601.2.1.0.256.27
Locale ID: 1033
Additional Information 1: 0a9e
Additional Information 2: 0a9e372d3b4ad19135b953a78882e789
Additional Information 3: 0a9e
Additional Information 4: 0a9e372d3b4ad19135b953a78882e789

Just before the crash, I get this logged in the console:

Starting C:\Qt\Qt5.6.0beta\Examples\Qt-5.6\qtwebengine\webenginewidgets\build-demobrowser-Desktop_Qt_5_6_0_MSVC2013_32bit-Release\release\demobrowser.exe...
[0215/190316:ERROR:gles2_cmd_decoder.cc(12613)] [GroupMarkerNotSet(crbug.com/242999)!:1460E40B]GL ERROR :GL_INVALID_ENUM : glTexStorage2DEXT: <- error from previous GL command

So it seems like maybe an OpenGL ES bug is behind this? I absolutely cannot get any browsers to load anything without crashing.

Installed in C:/qt/...
Added PATH to qt's bin folder.
Ran examples from Qt Creator.

Note: had to run in Release mode, because in Debug mode, I get an error saying it "could not find or load the Qt platform plugin "windows". Not sure why running in Release avoids this issue. I'm fairly unfamiliar with Qt Creator – I normally build with Visual Studio, but am using Qt Creator to test the examples.