I set up a site for my office that uses SSL encryption, but for some reason users can only see the site using IE. In Firefox, users see this error message:

Data Transfer Interrupted

The connection to [snipped] was interrupted while the page was loading.

The browser connected successfully, but the connection was interrupted while transferring information. Please try again.

* Are you unable to browse other sites? Check the computer's network connection.
* Still having trouble? Consult your network administrator or Internet provider for assistance.
Other non-IE browsers display similar messages.

Does anyone know why this is happening, and what I can do to make the site accessible to non-IE users?