JIRA Activity Stream gadget is broken when accessed externally using IE

1) Set up two Atlassian apps (I used JIRA 4.1 final and Confluence 3.2 final).
2) Add Confluence as an OAuth Consumer to JIRA.
3) Add the JIRA Activity Stream gadget to the External Gadget list in Confluence.
4) Insert the gadget onto a Confluence page and view it using IE.

The following behaviour occurs...

• Before authentication:
  • IE6/IE7 - the activity stream shows "No activity was found", even if anonymous access is enabled.
  • FireFox/IE8/Safari - the activity entries are displayed as expected.
• After authentication...
  • IE6/IE7 - a JavaScript error is thrown - "'null' is null or not an object" and the activity stream gadget is blank, except for the cog icon.
  • IE8 - the activity stream shows "No activity was found".
  • FireFox/Safari - the activity entries are displayed as expected.

Or for a visual summary, please see the attached screenshot collection.