Help with OpenGL, X-Axis as Time

I'd like to use opengl as the renderer because I want to add translucent patches to my plots, however I'm having trouble with the plots when the x-axis is in time. Here's my example:

x = now-1:1/1440:now;

y = rand(length(x),1);

H = figure;

I = plot(x,y);

set(H,'renderer','opengl')

This causes the lines to become unrecognizable, and unrepresentative of the data. However if I change from a line to a marker:

set(I,'Marker','.')

The data is now represented again. Which is a bit of a solution, just plot without a line, but I'd like the option of having a line for my data. Does anyone know why the opengl affects the plots like that, or how to fix it.

Just as an added note if the x-axis is not in date form (or not huge numbers maybe?) you don't get the same effect. Can opengl not handle large values?

Finally, if opengl will not work as a renderer for plots with dates as the x-axis, does anyone have any ideas of how to add a translucent patch over an area of a plot?

Thanks.