Cannot access secure area of Admin panel

[collig]

I can't access the secure area of my Admin panel! I'm able to log into the main page, which is unsecured, but when I click on any of the links to go into the secure part of it (catalog, customers, etc) I just get an error page saying IE cannot display the webpage. I haven't made any changes to the website in a while but have been using the Admin panel without any issues until several days ago (could be more, I haven't tried opening it in about a week).

Does anyone have ANY idea what this could be?! This is a live shop and I would hate to annoy potential customers by not keeping my store current.