QtScript debugger starts up slowly on Windows with 4.6.0

This is a regression from Qt 4.5.3.

When starting the QtScript debugger from Visual Studio using the following code

QScriptEngineDebugger debugger;
debugger.attachTo(&engine);
debugger.action(QScriptEngineDebugger::InterruptAction)->trigger();

then it starts up slowly (more then 10 seconds) with 4.6.0. This problem does not occur with Qt 4.5.3. The problem does not happen when running the application from the command line.