Rookie Q: I send from FCP to STP, but I can't save

Hi, and thanks in advance for any help.

I was in the Apple store, and unfortunately got a great tutorial on THEIR computer instead of my MBP (OS 10.4.11), and I can't figure out what I must be doing wrong. Using FCP Studio 2, control-click on clip, choose "send to STP Audio FIle Project, it opens in STP, I do removal of hiss, or Set Noise Print, then Reduce Noise, and it sounds great. But when I go to save, I get error message "THe document -name of file - could not be saved". When I return to FCP, the clip's audio now reads the clip name, with "(sent)", but it sounds NO DIFFERENT!

What gives?!

Thanks so much,
Reuven