I tried Firefox and the same thing, graph flashes. I have upgraded to 1.12.2 .
By flashing I mean the graph area blanks out and then a new graph appears.
I have the Lava lamp icon, a dial gauge and a thermometer icon displaying the same two random points and these images do not flash. The update rate is not as fast as the flashing of the graph.
I tried the Sample.jsp page (provided in the Mango install) and it does not flash. I have 3 static points and then a plot with 2 randomly changeing points, the same ones I'm using on the Mango graphical view page. I just added my data points to the sample page.