Firefox loads page, but not IE?

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I regularly visit a web page called http://www.constantcontact.com/index.jsp, which has always worked ok in IE. Now it won't load in IE. The front page works fine but when I try to log in it doesn't work. It will load about 20% of the top of the page and then just hang.

I've installed Firefox and this works fine now in Firefox but not in IE still?

Thanks