SL does tend to be unstable, some areas of the grid are more stable than others.
Usually, I keep upgrading my viewer until I get one that works for me. (They seem to release a new one sometimes as often as every few days to a week). Once I've got a stable build of the viewer, I keep it until they force an upgrade on me.
This may be helpful--or may just be my imagination--but it seems to work better for me if I have the latest drivers and OpenGL for my video card installed.