QThread + QTimer + skype4Com throws exception

Hello, fellow programmers. I`m trying the next thing:

I`m importing SKypeAPI dll Skype4Com and i`m trying to make a call in a new thread, wait 5 secs and finish the call and close the thread. The program is approved as a plugin before placing the call while the program starts. The problem is:

when i click "CALL" and point the mouse pointer outside the GUI.. when the timer kicks finishing the call -> the program freezes and throws some exception... BUT if i make the call and point the mouse to the GUI and click on some tab or even point a tab... when the call finishes, thread exits without freezing the main program. Threads and events are new for me and i`m struggling... do you know what am i missing? Here is some code:

sms.cpp -> from here i call the new thread

Code:

void SMS::SkypeCallInNewThread()
{
	// create new thread (on heap) and start it
	SkypeThread = new MyThread(this);
        SkypeThread->number = "echo123";
        SkypeThread->start(); // after this, thread's run() method starts
        connect(SkypeThread, SIGNAL(finished()), this, SLOT(SkypeThreadFinished()));
 
}
 
void SMS::SkypeThreadFinished()
{
    qDebug() << "Skype thread finished";
    SkypeThread->deleteLater();
}

myThread.h

Code:

#ifndef MYTHREAD_H
#define MYTHREAD_H
 
#include <QtGui>
#include <QTimer>
#import "Skype4COM.dll"
 
using namespace SKYPE4COMLib;
 
class MyThread : public QThread
{
	Q_OBJECT
 
public:
	MyThread(QObject *parent);
        void run();
	QString number;
 
private slots:
        void cancelCallfromSkype();
 
private:
        ISkypePtr pSkype;
        ICallPtr pCall;
 
};
 
 
#endif

mythread.cpp

Code:

#include "mythread.h"
 
MyThread::MyThread(QObject *parent)
: QThread(parent)
{
}
 
void MyThread::run()
{
	QByteArray ba = number.toLatin1();
	_bstr_t s = ba.data();        
        try{
        CoInitialize(NULL);
        pSkype.CreateInstance(__uuidof(SKYPE4COMLib::Skype));
        pSkype->Attach(6,VARIANT_TRUE);
        pCall = pSkype->PlaceCall(s, L"", L"", L"");
    }
        catch(...){
        qDebug() << "exception....";
        }
        QTimer *exitTimer = new QTimer();
        connect(exitTimer, SIGNAL(timeout()), this, SLOT(cancelCallfromSkype()));
        exitTimer->setSingleShot(true);
        exitTimer->start(5000);
        exec();
}
 
void MyThread::cancelCallfromSkype()
{
    try{
        qDebug() << "Stopping the call";
        pCall->Finish();
        qDebug() << "Call stopped...";
    }
    catch(...){
        qDebug() << "Exception....";
        }
    pCall = NULL;
    pSkype = NULL;
    CoUninitialize();
    quit();
}

When executing pCall->Finish() and the mouse pointer is outside the GUI... main program freezes and throws an exception. When i place the call and point mouse to the GUI and click something... pCall->Finish() executes and thread is exiting. Any idea?