Exactly which DLLs (full paths) are you copying from the Qt SDK to deploy? You should be using the files from:
QtSDK/Desktop/Qt/x.y.z/compiler/bin/ // for Qt core libraries
QtSDK/Desktop/Qt/x.y.z/compiler/plugins // for Qt plugins
QtSDK/Desktop/Qt/x.y.z/compiler/bin/ // for Qt core libraries
QtSDK/Desktop/Qt/x.y.z/compiler/plugins // for Qt plugins
To copy to clipboard, switch view to plain text mode
where x.y.z is the Qt version you built with and compiler is "mingw" if you used the bundled MingW compiler, and something else for each of MSVC 2008 and 2010. You must use the files matching the compiler you used to build your application. You deploy the release (i.e. QtCore4.dll, QtGui4.dll) libraries to match your application built in release mode.
You definitely do not want the Qt dlls from the QtSDK/QtCreator directory. They are the libraries against which the Qt Creator was built (probably with MSVC) and may not match your program (certainly not if you used MingW).
Bookmarks