Qt Creator example projects crash in unkillable state

Recently, I have encountered several Qt based applications that seem to crash with their processes in an unkillable state in Windows. When I try to create a new project, run an example project, or compile and run several of my existing projects they hang Qt Creator on compile. I can compile and run in debug mode just fine. Compiling in release mode works some times, but compile and run doesn't work for those projects. When I kill Qt Creator, it's process stops but the three child processes with the name of my project remain in an unkillable state. Other projects work fine. What should I be looking for?

Update:

I used to be able to use the compile and run feature in release mode in Qt Creator. Now, for some reason Qt Creator doesn't seem to link the plugins, platform frameworks, and .dll files necissary to run. I am using Qt 5.5.1 mingw on Windows 7.

If I use compile and run on a project in release mode, Qt Creator locks up and stops responding. The compile progress bar is about 50%, and I see three processes spawned in procexplorer with the project name. If I end program on Qt Creator, it shuts down but the three processes stay running. Taskkill returns success, but the processes are still running and have the project .exe file locked. The only solution is to restart.

My questions are:
Why does Qt enter this state when certain linked libraries or plugins are missing?

How can I get Qt Creator to dynamically link to the correct files like it used to when using compile and run in release mode