Qt Creator Crash ASSERT: "bitmap" in file image/qnativeimage.cpp, line 117

I'm getting crashes on Windows 7 64-bit. I tried building Qt Creator and running it via itself, and was able to see the follow assertion failure. Unfortunately I haven't been able to get a usable stack trace yet.

ASSERT: "bitmap" in file image/qnativeimage.cpp, line 117
LEAK: 231 Structure

I also see a bunch of these messages:

QThread::start: Failed to create thread (The access code is invalid.)

Both the version I've downloaded and installed and the one I've built myself have this problem. I'm building with mingw gcc 4.6.2