QProgressDialog stucks

[Mystical Groovy]

Hey everyone I want to use a progressdialog in busy mode to run a process

heres the code:

QProcess *installproc = new QProcess(this);
 
        QProgressDialog progress("Installing Package...", "Cancel", 0, 0, this);
        progress.setRange(0,0);
        progress.setWindowModality(Qt::WindowModal);
        progress.exec();
 
        installproc->start(InstallPkgCom);
 
        if (installproc->waitForFinished())
        {
                    progress.close();
        }

QProcess *installproc = new QProcess(this);

        QProgressDialog progress("Installing Package...", "Cancel", 0, 0, this);
        progress.setRange(0,0);
        progress.setWindowModality(Qt::WindowModal);
        progress.exec();

        installproc->start(InstallPkgCom);

        if (installproc->waitForFinished())
        {
                    progress.close();
        }

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the problem is that the dialog isnt closing with the process is finished..
iv noticed that if i dont press cancel or do anythink on the dialog for about 10-15 secs, and then press cancel, the dialog closes and the process is finished

so basically the process is running just fine even after the dialog shown up, but the dialog refuses to close when the process is finished.

p.s sorry for my english :P