Qt Plugins don't work on Windows Server 2003

Hello,

Custom plugin don't work on Windows Server 2003/2008 only (work on windows desktop).
Software to test:
http://files.first-world.info/ultracopier/1.0.1.12/ultracopier-windows-x86-1.0.1.12-setup.exe
http://files.first-world.info/ultracopier/1.0.1.12/ultracopier-windows-x86_64-1.0.1.12-setup.exe
I can't determine the problem, the error say only: Unknow error.
Plugin: CopyEngine/Ultracopier/copyEngine.dll, linked with Qt Core, Qt Gui, Qt Widget, Qt System Info.
Build under mingw.
The code:
newItem.pointer=new QPluginLoader(newItem.pluginPath);
QObject *pluginObject = newItem.pointer->instance();
if(pluginObject==NULL)

Depends.exe show the dependencies are ok on the plugin.
The other plugins just need be linked with QSystemInformation.
Cheers,