Are there any powerflyer software updates? Occasionally there's FastATA software updates. Wasn't the powerflyer from the 90's? Mike's right though, HDToolBox should see it. Have you checked the master/slave jumper on the CF adapter? Have you checked the CF adapter on anything else (like PC or A600/A1200 IDE)?
Edit: Okay, I see now that the old 4GB card works fine with it. That sorta rules out the adapter like you say.
On my FastATA there's different transfer modes that can be selected. What kind of config options are in your powerflyer prefs?