Update (8/4/2014): I have created a tutorial on how to create a ThinApp package to help get around this, check it out!
This morning it came to my attention that my customers were no longer able to upload any media (OVFs or ISOs) to their vCloud catalogs. This seems to be due to the most recent Java JRE version released by Oracle. The behavior I experienced was that the applet would appear to load but when I would click on the browse button nothing would happen. This happens across all different browsers and browser versions. The reason for this seems to be a change in the requirements for certificates and applet signing in JRE 7uU51.