Ok here ya go:
http://files-upload.com/files/621536/plotplugin.tar.gz

Qt 4.3.2 and gcc 4.1.2

Once extracted the src dir builds the plugin, the demo_src dir then uses the plugin.

Once compiled and running you will see two plot areas, the top area uses an Annotation without an initialized Line while the bottom uses an Annotation
with an initialized Line.

If you click the big printer icon a print dialog appears allowing you to select a printer.

If you print in Linux the plot areas will print correctly, if you print in Windows the bottom area will appear black because it's scene has a Line added to it.

I haven't tried painting it to a pixmap or anything just yet but I will get on that and post my feedback.