Heap block at .. modified at .. past requested size of - c++

Question

I try to create a window in another window with Qt and delete the first window. When the second window is opened the first window is deleted but when I try to delete the second window I get this error:
HEAP[Flash-TestBench-Client-Rev1-0.exe]:
Heap block at 18FBC298 modified at 18FBC2C4 past requested size of 24
Here is my simplified code:
main.cpp
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
ConnectionWindow *w = new ConnectionWindow;
return a.exec();
}
connectionwindow.cpp
ConnectionWindow::ConnectionWindow(QWidget *parent)
: QMainWindow(parent)
{
QWidget *w = new QWidget;
QVBoxLayout *l = new QVBoxLayout;
QPushButton *button = new QPushButton;
button->setText("Connect");
conenect(button, SINGNAL(pressed()), this, (openW()));
l->addWidget(button);
w->setLayout(l);
this->setCentralWidget(w);
this->setAttribute(Qt::WA_DeleteOnClose);
this->show;
}
void ConnectionWindow::openW(){
MainWindow *window = new MainWindow;
this->close;
}
mainwindow.cpp
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
QWidget *w = new QWidget;
QVBoxLayout *l = new QVBoxLayout;
QPushButton *button = new QPushButton;
button->setText("Close");
conenect(button, SINGNAL(pressed()), this, (closeW));
l->addWidget(button);
w->setLayout(l);
this->setCentralWidget(w);
this->setAttribute(Qt::WA_DeleteOnClose);
this->show;
}
void MainWindow::closeW(){
this->close();
}