ich have written a multi thread program, it`s used to draw Elipses,
there are three buttons in main Thread Frame, "Start A", "StartB" and "Quit".
if i press "StartA", it will draw Elipse A in a QLabel, press "StartB" draw Elipse B.

But by runing, if i press "StartA" or "StartB", a error occurs as follows:

Microsoft Visual C++ Runtime Library(titel)
Runtime Error
...
This application has requested the Runtime to terminate it in an unsusal way.
Please contact the application`s support team for more information.

my develop environment is Eclipse+ MinGW+QT4.4.0(open edition)

what is wrong with it?

thanks for your Help!