Hi Gene, and welcome to WXforum.net!
The issue with IE9+ and the rotate-the-image captcha is well known and can be 'avoided' by instructing IE to access the website in 'compatibility mode', then the images will rotate as the sliders are moved. It's an IE issue (as you said) as Chrome, Firefox and Opera have never had the issue. On the
info page (linked from the registration page) shows, IE users need bot "compatibility mode" and JavaScript enabled for the site to successfully complete registration
I hope you enjoy your stay with us, and thanks for the feedback.
Best regards,
Ken