JSON in Addresses breaks Drupal fieldsets in IE

After upgrading to the latest version of Addresses (6.x-1.12), we noticed an odd phenomenon when using Internet Explorer (specifically: IE7, IE8 & IE9 on Windows XP and Windows 7). When attempting to add or edit a node that includes an "Addresses - CCK" field, we discovered that the collapsed fieldsets on the page didn't work. Common fieldsets like "Menu settings," "Input format," and "Publishing options" were no longer expandable — clicking on the fieldset label yielded no results. All the fieldsets on the page looked and acted like plain, flat text. NOTE: This phenomenon only occurs when a content type includes an "Addresses - CCK" field. All the rest of our content types behave normally. Previous versions of Addresses didn't have this problem.

Using IE9's developer tools (F12), I discovered that a JSON error was being produced:

SCRIPT5009: 'JSON' is undefined 
addresses.js?V, line 33 character 5

Looking at addresses.js and comparing it to the same file in the previous version of Addresses, I saw that the line "'attributes':JSON.stringify(attributes)" was added. Removing that line solved the fieldset problem — the fieldsets became clickable again, expanding and collapsing as they should.

However, I figure removing that line isn't an option, especially since this problem seems isolated to Internet Explorer.

At the top of addresses.js, I added the following code:
if (!JSON) JSON = {};

This ensures that JSON has a value, even if the browser hasn't declared it for some reason. Adding that line *does* solve the problem in IE (fieldsets become expandable again), although an error is still produced:

SCRIPT5009: 'JSON' is undefined 
addresses.js?V, line 9 character 1

Can you think of a better, more official way to resolve this problem — one that can be added to the module in the future?

Thanks!