use toast
I had the same problem, until I used toast 7 to make a bare bones iso 9660 image:
-under the 'data' tab, select 'iso 9660' in the pane on the left
-drop your files
-click 'select'
-click the 'settings' tab
-set 'format' to 'cd-rom', 'naming' to 'iso 9660 level 1' and uncheck...