Ok - as an update..
I remembered about the logs that it provides, so I looked through there - I had a total of 80 registration attempts on one of my sites today.. of that 80, it let 4 through.
The 4 were from the same IP address, which is in the stopforumspam.com database 57 times so far..
My API code currently does point to
www.stopforumspam.com and not api.stopforumspam.com but because of the 76 blocks today it seems to be contacting the server fine..
I did just change the code to what you have pasted above and will see how it goes over the next couple days..
Thanks,
Rob