You can't mix the DLLs from different sources / built with different compilers (that's not a general rule but the VC++ / MinGW compiled Qt DLLs use different run-time libraries)... anyway, you have to start it from the build directory with the same environment as for the compile, so enter "release\qmc2-mame.exe" from there and it should work fine. If you want to "deploy" it to some directory, see here.

A mind is like a parachute. It doesn't work unless it's open. [Frank Zappa]