I'm working with a client who is trying to use our software, which accesses information (sends & receives) from a third-party website. When this client tries to access these pages, a window opens, as expected, but is completely blank and no error message is received. This is the first time I've seen this with many other clients successfully using this product, which leads me to believe that it has something to do with the settings on the computer somewhere, but cannot figure out what might be happening.

Windows Server 2003 R2, Standard Edition, Service Pack 2. Firewall is already off. Tried AVG on & temporarily disabled.