Digital BW, The Print

There could be anumber of possible reasons, but without knowing more 
about your particular setup I would look at a memory/spooling error 
to start with. Try turning off spooling/background printing. Also, 
try printing at different image sizes and resolutions to see if the 
problem is aggravated by larger file sizes.

Photoshop problem -- I've had that occur periodically, usually a 
reboot clears it up. Try saving the file to a different location. 
Also see if your scratch disk(s) are all filled up, if so try 
Edit/Purge/All (losing any possibility of undo/history).