Brush in Storyboard Pro lagging/dashed line...


I just got a new iMac 4 GHz Intel Core i7 and my brush line in TB Storyboard Pro (V. 8.0.1 - 2007) is
lagging and has a dashed line for a second or two before the line becomes intact/solid.

You can see a video that I took of it by clicking here:

Any ideas how/why this is happening?
If so… Any ideas how to fix it?

Thanks in advance.