Make sure you are not using mingw, but mingw-w64. mingw is more or less dead nowadays.
My recommendation is to use the mingw-w64 packaged in the latest Qt SDK. There is a Qt-builds project as well other than the mingw builds. That is run by the mingw-builds team. They have proper scripts to build all of Qt, QtCreator, and so forth.
Here you can find them (develop branch):
https://github.com/Alexpux/Qt-builds/tree/develop
That being said, you can grab the latest for today with mingw, too:
https://code.google.com/p/psi-dev/downloads/detail?name=MinGW-gcc-4.4.0-2.7z