When zooming in "too much" there seems to be a problem when (re?)drawing.
This occurred when using a XYLineAndShapeRenderer/XYPlot.
The axis are both number axis.
Don't get confused by the "time"-label on the x-axis.
I added 3 screenshots (screen1-3.png) for demonstration.
The interesting thing is:
When using the internal methods to save the graph to disk (menu -> Save as) the saved image is not(!) broken (export3.png).
Workaround: Don't "allow" to zoom in "too much" (add listeners to both axis and limit the minimal range displayed on each axis).
version: jfreechart 1.0.9 SWT