The error message from IE
Internet Explorer was unable to open this site. The requested site is either unavailable or cannot be found. Please try again later.
The fix...
# before calling send_data
response.headers.delete("Pragma")
response.headers.delete('Cache-Control')
This issue is not restricted to rails, any server side code that sets no-cache is subject to the same issue. Glad I was able to find this post.
see also kb-316431