Forget the website, just call the TransUnion Freeze hotline 888-909-8872
Edit: since this blew up
If you can't get through try calling at a weird time when the volume might be low. E.g., 12:30AM
Here are the other two credit union freeze hotlines:
Equifax: 1-800-685-1111 (NY residents 1-800-349-9960)
Experian: 1 888 397 3742
While you're at it you might as well opt out of promotional solicitations from credit unions too www.optoutprescreen.com.