This does sound like a driver issue as previously mentioned. What I am curious about is this. Doesn't this Motherboard MSI K7D use the AMD 762/768 chipset? and do you have the AMD drivers for both installed along with the Amd Eide Driver?. Not the Via drivers.
I think you might find a clue as to what is happening, by checking the Event Viewer in Administrative Tools. Specifically check the application and system sections during the time you did those burns.
Each application should hopefully leave an error log. Maybe you will be able to determine what is happening. It may be a mixture of several things.
Anyways, Just a thought:)