Grids don't appear in popup window

I have an htm file with a grid that works when it is opened in a browser window but not in a popup window. The code I have in the parent window to spawn the popup window is as follows:

function popupa(mylink, windowname)
{
if (! window.focus)return true;
var href;
if (typeof(mylink) == 'string')
href=mylink;
else
href=mylink.href;
window.open(href, windowname, 'width=800,height=600,scrollbars=yes');
return false;
}

The link is to a .cgi file that dumps the content of the .htm file in the popup window. The grids don't appear and there are no error messages (again, it works fine when I open the same .htm file in IE).

Any ideas?

Thanks