What you are seeing is dropouts of your digital signal going to the recording unit. I have this problem somewhat myself at times, especially on pieces longer that 4 or 5 minutes. It could be a hdwe compatability problem between the 2 digital units and/or a firewire card compatibility problem. Mentioned in another thread, make sure you disable all programs not needed except explorer and systray. That will free up the most memory and resources for you.

good luck
dave