screenshot of graph does not show functions

Using the "Screenshot" function under the graphics tab in lubuntu 12.04.1 results in the output showing the Cartesian grid, and any drawings I've done on the grid, but no functions.

That is, anything done with the paint and text tools remains on the screenshot, but none of the functions I've graphed show up. Also, after taking the screenshot, the functions disappear from the graph window and must be redrawn using the "print" button.