Signal/slot responsiveness

[guiQt]

Testing QClipboard class, i wrote:

clipboard = QApplication::clipboard();
connect(clipboard, SIGNAL(changed(QClipboard::Mode)), this, SLOT(clipboardChanged()));

clipboard = QApplication::clipboard();
connect(clipboard, SIGNAL(changed(QClipboard::Mode)), this, SLOT(clipboardChanged()));

To copy to clipboard, switch view to plain text mode 

After an initial proper behavior (10-15 times clipboardChanged slot called after every data change ), app stops working (clipboardChanged not called anymore ).
Any suggestions are greatly appreciated.