about:blank and Microsoft Internet Explorer Enhanced Security Configuration issue

Happy

Hi there,
I am having a small problem with the run and frameset modes of the BIRT-Viewer.

I need to deploy the reports onto a locked down environment (using IE6 configured with Microsoft Enhanced Security Configuration).

The issue I am having is that the run and frameset modes generate pop-up warnings saying the content has been blocked (see below picture)

Now, if I add the location to the list of trusted sites I get no issue;
If I do not add it, none of the client side javascript I have created seems to work.

What I would like to understand is where this about:blank warning is likely to come from and if there is any way I can modify BIRT or the report designs to prevent it from appearing in the first place.

Cheers