I wonder if someone could help me with an issue I'm having playing back video?

Whenever there is any fast moving video, I get an effect like the screen below:

Click image for larger version Name: ati-scan-line-problem.jpg Views: 426 Size: 52.3 KB ID: 6039

I have tried several media players (including VLC and media player classic and home cinema). I have re-installed, and also upgraded graphics card drivers. It happens on both SD and HD clips.

Any ideas?

My PC:

AMD 2.7Ghz dual-core
Win 7 x64
Ati Radeon HD 5450
4Gb ddr2 ram
50" LG plasma tv