looks like your GPU is f*** up.
Please try to use Threads
That might be an issue of the GUI Thread hanging because you messed up something at another corner. Therefor the GUI is not redrawn correctly.
You can add a Thread to your Dialog factory (if you have one or at least a centralized point to launch the Dialogs).
But I guess you have a far bigger problem - something ruins your GUI Thread... How is the RAM load? Does the application run into a heap space? I bet so.