@multisil: Thanks, it works... but the Segmentation fault comes anyway

I have taken your GPSConnection class unchanged, and initialised it in the way you have done it in the second file. My stripped down application window has a single QListWidget and opens QMessageBox on demand. The application works flawlessly unless I allow start of GPSConnection thread, only start, NO data manipulations. Within a minute or two of using QListWidget and QMessageBox there comes SIGSEGV.

Sorry it does not work in my case, but thanks anyway for the idea and sort of working example.