32-bit Qt application on win 7 x64 won't run, but runs fine from Qt Creator?

My somewhat educated guess would be that your application can simply not find the required DLLs. To be sure, you could open your exe in Dependency Walker to see if it finds all the necessary DLLs. If nothing seems amiss at first, then use Dependency Walker to profile the application. This might reveal some missing dependencies loaded at run-time.

If this relates to your Qt DLLs, make sure that there is either an appropriate entry within your PATH environment variable, or that the required DLLs are included in your EXE's directory (though the latter might not be the best choice on a development machine).