I am not able to print my drawings half size anymore.  For example, I am trying to plot a 24x36 sheet to a 12x18 sheet. I do the normal procedure for plotting, I set the plot scale to 1:2 and I tell the plotter to use a paper size of 12x18. The plotter then spits out a 9-1/2x18" plot. There must be some setting that got changed. Very frustrating. I am using AutoCAD 2012.

Is the plot centered?Are you plotting "Extents" vs. Display for example?

The whole drawing is printing, the program is just plotting the drawing at a very small scale (disregarding the scale I told the program) in the corner, not at half size.

Are you plotting from model space or from a layout?

layout.

Post a print screen image of your plot dialog box.?