David 
Hi everybody! I have written a good program; by the way I suppose it. After about 10 minutes my program got frozen. (I don’t know the exact English word for blue dead. ) I mean the GUI stopped do anything. “Everything is dead”. I have started to check lot of things. I have been doing it for a while. Until yet I haven’t reached any success. What should I do too? Some feature from my program: It contains about 5 QThread base classes, serial communications, really complex GUI with 6 big Form. I have also made my own screensaver. I also use three timer in three different classes. I didn’t give attention for parallel threads. Could it be the problem? I suppose communication is good because of qextserialport project. Any ideas for checking would be appreciated. :-) David