Response:

What is the video hardware? Is that common between malfunctioning devices?
Mostly common but not all. All desktops had the problem but one laptop also has the problem. Desktops have Plug and Play Monitor. Display adapter "Intel(R) 946GZ Express Chipset Family".

What is the video driver version? Is it the latest available? Is that common between malfunctioning devices?
Video driver version is not the latest but is common between malfunctioning devices.

What is the operating system? Is that common between malfunctioning devices?
OS is XP SP2. Is common among all devices including the ones where it works.

Does the problem persist if you start your application with the software raster renderer? (Should be the default on Windows but worth a try)
I will try this.

Thanks for your advise, based on that I will try updating the driver etc. I am also hoping for something within QT that should fix this problem.

Anil