After copying the text provided for installing PF, there are 3 lines that I think should be changed. They are the lines that contain "-auxww." I am running Mac OSX 10.5.2 and I think this problem showed up about the time I upgraded to 10.5.
If I manually execute "ps -auxww | grep popfile.pl | grep -v grep | awk '{ print $2 }'" in the Terminal, I get "ps: No user named 'xww'."
If I change the line to read "ps -axww -u root/*OR USERNAME* | grep popfile.pl | grep -v grep | awk '{ print $2 }'," in both instances the pid was returned. Both were same pid, natch!
HTH