Hi Thomas,
Sorry to hear this.
Can you look around your web space for error_log both in the root of your website, and under wp-admin folder.
Can you look within (at the end of) those error_log files for something relating to wp-simple-firewall and post them here.
My guess is there's a function or something being run that your hosting doesn't like.
Once I find the error, I can work around it.
Thanks!
Paul.