After a fair bit of work (and money), I have now updated the code signing certificate used for the FFB Client. This means that people with very strict security settings will be able to run the client yet again.
For everyone else, this means that there will be a new download of the FFB Client next time you spectate or start a match. In some circumstances (ie, if this takes too long), you will get a "Wrong Password" dialog. If this happens simply close the client and relaunch and things should be back to normal again.
Thank you for your patience!