Ok, after one try with no answer at all and a second try with only a completely unrelated answer, here goes my third try:
Where can I set the halftone print screen settings?
In Photoshop CS4 these settings could be accessed by a button in the print dialogue, but this button is gone in Photoshop CS5. Below the screen shots of the two print dialogues (with otherwise identical settings):
The print dialogue of CS4 with the "Screen…" button (red circle)

The print dialogue of CS5 where the button is missing.
