Sam, a white screen is an indication that you may not have Java on your PC, or, a more likely problem is that it may not have installed correctly if you updated it.
- Uninstall Java and re-install it (or install it if not already installed)
- Restart your PC
Then try to spectate a race in the free viewer.
If it doesn't work let us know!
Another solution may be that if you updated Java (or have not used it in a long while) and you did not leave the free viewer page open for at least five minutes (maximum ten minutes) then Java did not get a chance to begin loading. This is rare, but does happen.