Most of the time I try to add a motion blur to this animation, it gives me an error message, and closes out Synfig. It happens a whole lot. When it does open, If i try to tweak its settings, it closes. Sometimes it closes just for motion blur being checked. 
I am using Windows version.
Can you post a simple offending file? Thanks for report the problem.
-G
sure thing. here it goes.
Hi,
I don’t notice any crash or weird behavior when checking or manipulating the Motion Blur layer.
Windows XP Synfig Studio 0.63.01.
It is only the Subsamples Factor which can cause a problem because it will increase rapidly the render time when you increase it from 1.0 (default value) so insane values might break something. Setting it to something smaller than 0.0 will speed up render. Just replace the desired value before render the scene to the master copy.
Quality settings is also affecting to motion blur but it is affecting to all the rest of layers too that might be you don’t want to have that.
-G
Maybe it’s my computer then. I still crash. 
Usually I have the quality at 8 when I work on the canvas doing the project. When rendering it, I put the quality of the frames at 9. You know, I was wondering why the motion blur was looking funny. I forgot that lower is better. Thanks for the reminder 
.
If its the computer, then I will have to activate motion blurs until I’m ready to render. Either that or change the quality to 10.0.