HS widget frozen/disabled after hitting the back button

Issue Summary

I have a regular taxonomy term in an exposed filter on a view. I use filterblock module to show the filter on the front page. One of the fields in the exposed filter is a taxonomy term with a 2 level hierarchy. HS is setup so to allow the user to choose a term at any level in the hierarchy, and multiple select is not allowed. The widgets show up as dropdown lists. If I fill in the filter form, hit submit, I am taken to a results page (no filter block on the results page, by design).

The problem occurs if I then hit the back button to get back to the filter form. The following happens upon return to the filter form page:
- The HS widget on the form shows up grey and is disabled, I cannot change the value.
- Regardless of whether I had chosen a first or second level taxonomy term, the only widget showing is the greyed-out first level term, and it displays the term I had chosen before hitting the submit button.
- If I hit the "reload the page" button on the browser, I get the same problem
- If I navigate to the url for the "broken" page, the problem goes away and the HS widget is reset.

Please let me know if you need more information.

thanks,

Steve