rendering error

Support Basics & Interface
1

I became a Blender user last week, I’m glad. But I have a ploblem.
During ray tracing rendering, I get a few random error frames on specular&transparent objects like below.
http://www.ateliermuurie.com/pm/render_ploblem01.htm
How can I do?
I use Blender 2.41

2

Not that this would cause the problem, but why do you use 2.41 instead of 2.42?

3

I was looking for the parameters to control for ray bounding times or something. But after installing 2.42, the problem’s gone, …I think.
THANKS.