I am using SVN 3875 (24/09/2010).
Spec: Linux, Sun Java 1.6.0_20-b02 64bit, 8 GByte RAM, Core2Quad 2,66 GHz (Q9450)
When using the arrow keys to scroll, the behaviour is inverse to what I know from other programs (e.g. inkscape). All computer games I know have a method to toggle inversion of this beviour (when using the mouse to look around in 3D), I think zgrviewer needs the same.