Images not displaying when I send tests in Outlook

I have never had any problems when testing my html emails, however in the last month when I send out the test email, it does not display my images in my Outlook. They show-up in my Yahoo! email though. The images also come through fine in my Outlook when I send the live email.

I checked with our IT department and they couldn't figure out why that was happening all of a sudden. Has anyone else had this happen? Anyone know of a way to fix it?