OK, I'm still using V10, but if anyone can confirm that this is fixed in CS I would be grateful.

Try this: in a new document draw a line at 45 degrees. Apply a stroke of .5mm (or less) and use the filters menu to add arrowhead number 21 (the dot) at 35%. Now zoom in and look at the the arrowhead. Toggle between overprint and knockout in the attributes panel. Observe how the dot alternates between being round and squared off.

Oddly enough, regardless of the overprint setting it still prints squared off even though it may look round on screen. The only fix I have found is to export artwork as a V8 eps (which has its own problems) before placing in InDesign or Quark. In any case the arrowhead does not adopt the overprint settings of the line regardless!

Incidentally, I use this to indicate a terminated road road in the maps I produce, and workarounds like drawing circles, or placing a symbol are not really options.

Thanks in advance

Andrew