Always check the settings in a browser when you upgrade- especially those for security.
It's most likely that IE8 has changed some setting- you will need to reset. As far as I know, when you use the "reset" feature for IE, it will reset everything on the browser, including the home page. Suggest checking security setting first for possible manual reset on one or more.
If FedEx is a secure site: Open Internet Options> Advanced tab> Security section> make sure SSL 2.0, SSLS 3.0 and TLS 1.0 are all checked. Your path might be slightly different as this is for IE6,