My entire active direcory had a password change this morning

When i came in today AD forced a password change on me. Normally i wouldn’t find this odd but i remembered that i never got a warning message that my password was about to expire. I asked several of my users if they had a similar experience this morning and they said yes.

What would cause my entire AD to have a password change?!?

Im on a SBS 2003 server with about 50 clients