windows parental controll, problem?

[TRMA18]

We have had a lap top for about a year now and have been using windows parental controls for the kids. We like it a lot and seems todo a good job. The problem is last night the kids tried to get on their favorite web sites (Which it has always allowed them before) and parental controls blocked them. Not all of them but most. I believe Yahoo mail still worked. I could go in and manually allow them and it worked fine. All of the admin accounts worked as usual. I am happy with IE and dont want to go with another browser. Anybody know what might have caused this problem? Could it be that those affected sites stopped broadcasting their WEB rating temporarily. Thanks in advance.