We are having a problem where a drawing suddenly won't print completely. (has been working ok for months)Drawing has several x-ref base files and the title block is xrefed into pspace and is being plotted from pspace, drawing looks fine on the screen but when plotted the title block and linework in the immediate drawing won't plot.  xrefs other than the title block are all that print. any ideas?

Are the missing parts displayed in the plot preview? This could have many reasons - layer set to non-plotting, not enough memory in the plotter, DWG coming from a non-Autodesk software (forged DWG), plot style table setting to "white-printing", etc.