I am having an issue along these same lines. Not a problem with the pop-up but with IE7 opening the document or saving it. Everything works as expected in FF (my default browser) but when I am prompted for open or save in IE7 I get the following response.
Open - I receive a blank IE page.
Save - Windows Internet Explorer message
"Internet Explorer cannot download Test.doc from... website.com
Internet Explorer was not able to open this Internet site. The requested site is either unavailable or cannot be found. Please try again later."
I know the site is available and that this works in FF.
Any advice on this one?
Thanks