Thanks for that Tarq57.
It's definitely freezing, not just temporarily stopping due to download speed. I should say that prior to the re-format/re-install it did play perfectly. RAM is 2.50GB, CPU is AMD Sempron 3000+. Antivirus is Avast! and
AFAIK graphics and display drivers are up-to-date.
I'm thinking that maybe I should go back to the drawing board and re-format/re-install again and perhaps try a different graphics card and hope the glitch goes away. I would prefer not to as it is all a bit of a hassle.