Did you get the stunnel off the twofo website? http://www.twofo.co.uk/resources/stunnel.zip Just extract the files and run stunnel.exe, you should not be installing anything as such. This is the ONLY version that will work for twofo.
If you did, try restarting stunnel on your computer, the server was reset earlier today so it may have just gotten stuck on that. If neither of those work, can you paste in anything else the log is showing up.