Before reporting a bug, please check the FAQ to see if the behavior you are observing is mentioned there.

If you encounter a bug not already documented, please send email to the LOCI software mailing list with a description of the problem, and if possible, a list of steps to reproduce it.

Keep in mind that VisBio runs using VisAD and Java3D functionality, which in turn take advantage of Java and OpenGL, which run within your operating system, so any bug you find could be anywhere within this hierarchy.