Mike,

Great news! I finally got it to work and you were right - it was due to the
headers. I discovered that IE would not repopulate form values unless
certain headers were set correctly. The three headers I had to set to get
it working were:

ETag
Cache-Control
Last-Modified

By default, Ruby on Rails does not set these headers on responses. Now,
here's the gotcha. The form I was working with was embedded in an iframe
within the main page and it turns out that IE refused to repopulate this form
even when I had the headers set correctly for the HTTP connection serving the
iframe content. Try as I might, I just couldn't get it to work. I worked
around this problem by setting up hidden form values in the main page and
using javascript within the iframe to get the data from the main page form
fields. It's kinda ugly, but it works.

Now our users can happily hit the back button on IE and our AJAX calendars
will return to the view type and date that they were at when they left the
page. I'm very happy. Thanks for your help!

Tyler