Can't capture a frame with Nero Showtime

Hi folks,
I have Nero 8 installed and i want to capture a frame from a running dvd.
But when i press the button to do so, the dvd stops playing and Showtime
stops completly. And than i'm back in Nero Smart Start again. I've told Nero
where he must put the file (i want it to makes .bmp) but no frames there to
be found.
I can make frames with WMP but i want to know what i'm doing wrong with
Nero. Can anyone help me please?
Thanks in advange!
Trudy